15 of us spent my wife's 40th in El Brasero in Los Christianos.
Had a brilliant night
The meal wasnt too bad either

I was in PDLA in December on my mates 50th.We booked a table at Montana's in PDLA for 18 of us.The meal was fasntastic and the atmosphere great.No music or anything but we entertained ourselves and also the rest of the customers in there.We were made very welcome by the staff.I would go and book a table when you get there if you fancy it.Its directly outside Parque Santiago 2 complex

I was at Tenerife at new year and had an amazing meal at a Mexican in teh Safari centre - next to harrys cocktail bar and the fountain - its called Hacienda Miranda - Grill & Tex Mex Restaurant
Good atmosphere with a singer on and they have the Hugest mexican hats for you to put on and have photos taken with, and of course theres the delicious food and cocktails!!
however if mexican isnt your thing in the same complex theres the following restaurants as well
Maria Bonita - Spanish Restaurant and Tapas Bar
Restaurante Sangre de Toro - Steak House
Harry's American Pie - American Restaurant
Slow Boat Teppanyaki - Oriental
Bianco - Italian Restaurant
Gran Reserva Restaurante - Steak House
Domvs Avrea - Trattoria

All in great setting - really classy but not too posh if that makes sense - if you do head here start with cocktails at harrys bar - then after meall head over the road to the Magic bar http://www.magicloungebar.com/ its fab with great singer on and brill atmosphere for all ages