I've been to La Salsa a couple of times now and both visits have been absolutely top notch. The last visit I was in a group of 10 from work and the service and speed was fantastic. Can't rate this place highly enough although I have never been on a Friday or Saturday night.
For any carnivores out there BEM Brasil in Manchester is well worth a visit. All you can eat Brazilian just off Deansgate. It's a bit like a BBQ delivered to your table - Lamb, Steak, Chicken, Sausages, Ribs etc all sliced straight from the skewer on to your plate. Not the cheapest but definitely worth the money. If you like a beer with your meal try the Brahma Brazilian bottled lager.