Yeah, it used to be better than it is now, but even then is was fairly standard inauthentic Mexican stuff - fajitas, enchiladas etc.
If it's Mexican you're after, try El Cartel on Thistle Street. Small place and they don't take bookings, so you're pretty much guaranteed a short wait, but they'll take your phone number and send you to the pub over the road until your table is ready. Really decent food in there.