They usually tell you when you're there but it's good to know that the carnitas is no spice, chicken is mild spice and steak is the spiciest! :) the mild salsa has jalapenos in it, so if you don't like spicy and you get mild sauce (the corn salsa) you may get a spicy surprise. But it's delicious!
I'd start with a burrito bowl just because its easier to eat. Afa what meat I would go with the steak. But if your prefer chicken or pork they are all great. Afa the salsa stick with the fresh one or ask for it on the side. In case you don't like the heat.
I would go for the classic burrito! I would say if it is your first time going, try to go at an off time. If the restaurant is busy they will often rush you along and it can get a little chaotic and confusing if you don't know exactly what you want.