Never Assume and if you do, assume the worst.
When you follow a plant based lifestyle, eating out in your home city is tricky enough so being in a strange city can cause some anxiety.
The best way to alleviate your stress is to research and plan ahead!
If you will be in a large city then your options will be plenty, a small town? Not so much!
You HAVE to ask questions. Never assume anyone knows what vegan actually means. You'd be surprised what people think is vegan.
One time I was told that the marinara was vegan because they removed the meatballs after they cooked them in the sauce! People think chicken and fish are vegan and no one ever thinks that broth is something you'd be avoiding.
Chain restaurants are going to be mostly off your list unless it's Native Foods Cafe or a similar vegan chain. Same with fast food. There are a few places you can get something that will tide you over but to get the really good stuff you will need to find the local ethnic restaurants.
Your first step should be to check for any local vegan places and if that is a no-go.. then read on:
Keep in mind that these places may go against your morals and beliefs since they serve animal products. You may not wish to eat there. I encourage you to check out the websites of various fast food places and make yourself aware of what items they have that are plant based so you are prepared.
Don't assume the veggie burgers or fries are ok (McDonald's adds milk and beef to their fries and Burger King's veggie burger is not vegan!). Plus, companies routinely change their ingredients so you need to double check frequently.
Always know what your options are. I don't recommend eating fast food crap unless you have no choice.
Most places have salads that you can order without chicken and cheese but most salad dressings will not be ok and will be filled with high fructose corn syrup. You could ask for lemon wedges or salsa for a dressing if you can't find an oil/vinegar selection.
Mexican places like Taco Bell usually have bean burritos, bean tacos and mexican pizza type products that you can request be made meat, cheese and sour cream free. Chipotle has white rice, black beans (the pintos have pork), salsa and guacamole that are all ok. I believe their tortillas, taco shells and chips are all safe.
Sandwiches shops like Subway, Quizno's and Jimmy Johns can be a little tricky. For example, at Subway, only their Italian bread is vegan and free from HFCS so I get that for my Veggie Delite sub. I get all the veggies, salt, pepper and mustard. Most of the sauces are mayo based and even the vinegar sauces can sometimes contain animal ingredients. If you are taking the sandwich back to your home base you can add slices of Tofurky or tempeh and a slather of Vegenaise if you were lucky enough to score some!
Again, the key to successfully navigating fast food joints is research. Make a list of each company and what they offer that is vegan. Carry it with you.
Generally, ethnic restaurants are your best bet but they can have hidden ingredients you need to watch out for.
Japanese - I've never been to a Japanese place that didn't have veggie sushi! If you're like me and you don't like nori (seaweed) then you can ask for Soy Wrap. The 5 sushi places in my small town all offer it so I'd expect to see it available elsewhere. I also like to get an order of veggie tempura. Most soups are broth based so check with your server. You can usually find yakisoba noodles and fried rice, just ask for no broth, no fish sauce, no eggs and no meat.
Thai and Chinese - our local places will sub in tofu for whatever meat is listed in a dish or you can just have the veggies. There may be a few appetizers that are vegan like spring rolls or fried veggies. Soups are usually broth based, so ask questions. Ask that they use no fish sauce, no MSG and no egg.
Mediterranean - hummus, falafel, and salads await you! The photo in this post is the veggie platter from our local Mediterranean place. The food is delicious. Soups usually have broth but you may get lucky. Just ask. At our local place, if we call a day ahead we can have soup made without the chicken broth.
Italian - cheeseless pizza, pasta with marinara sauce or tossed with veggies, herbs and olive oil, salads are usually safe. Call ahead to see if you need to bring your own salad dressing or Earth Balance for the bread. some sauces contain meat or cheese so ask some questions. I like to take along a jar of my vegan parmesan 'cheese' to sprinkle on my pizza.
Indian - I've never had Indian food but I've hard it can be vegan friendly.
Mexican - beans are your best friend, provided they aren't full of lard. So that should be your first question. generally, I'd go for the veggie fajitas but if the beans are safe you could do tacos or a burrito. The chips and salsa are almost always safe.
I try like hell to stay away from chain restaurants. However, I know it can be unavoidable on vacation.
Steakhouses - the shocking thing I've learned about these places is that they take innocent veggies and subject them to horrific treatment involving flesh and secretions. Baked potatoes slathered in lard before baking, bacon added to green beans, mushrooms and onions sauteed in butter and then left soaking in it.. the horrors are plenty. Even the breads aren't safe.
I usually get a baked sweet potato (plain) and put on my own cinnamon. You can also bring a little earth balance, maple syrup or sucanat if you want it sweet. I'll also get a salad minus the flesh and secretions. I bring my own dressing.
American - these are those places that have a little bit of everything on their menu. Places like TGI Fridays, Applebees and the like. I'm gonna say that probably you won't find much there. I can't even think of anything to suggest. You have to go online and search their website for ingredients. You may find salads you can change up or a potato choice but it's gonna be tough. I gotta be honest.
Breakfast places - the problem here is going to be butter, eggs and milk. You can ask if their pancakes and waffles are made with water or milk, if they are egg free but you will still need to bring your own Earth Balance and pure maple syrup. They will have flavored HFCS on the table. You could get hash browns and veggies but are they cooked in butter?
I'd go for the fresh fruit dish and maybe a slice of toast or an english muffin but again, ask about milk and the jam will be HFCS, I'm sure. They might have peanut butter tho.