The Peace Corps is very much a US government agency, and it carries plenty of baggage accordingly.
If you have a specific service you want to provide, or just a particular place where you want to help out, you'll probably have a better experience and be of better use if you sign up with alternative non-profit efforts.
If you haven't already considered it, you might look into shorter-term commitments/experiences through university anthro department programs, church programs, or organizations like Eurep. This way you might get a better feel for what you want to do. These types of programs aren't as wholly immersive as longer-term ones, which can make keeping a veg*n lifestyle more practical than otherwise.