I've never been to a Subway (they're not very common here), but looking at the "all sandwiches" thing on their website, it appears I wouldn't have much of a choice if I did as they seem to have an unhealthy obsession with meat and poultry; as a pescetarian, only their tuna and veggie sandwiches I could actually eat, which is lame. (Boooo!) No idea if they allow for customising them; the first post seems to imply that, but I cannot find anything related to that on their site.