It depends on your budget, but here's a few options.
Also Playa de Los Artiste is NOT in the middle of town - it is a 5-10 minute walk outside of town.
If you really want the middle of town (which can be very noisy at night:)
Sano Banano - higher end, more expensive
Mar y Cielo - nice rooms, around $35, no website, but I can get phone#
Aurora - I think around $40/double
Just outside of town near to the restaurant :
Amor de Mar
Just outside of town on the other side
Nightlife - there is really only Chico's Bar, it's quite nice during the day - there are tables out on the back lawn with a sea view, but I would never call it romantic - it can get a bit crazy at night. The only places I really would describe as romatic are the Playa de Los Artiste which you already know about and Ylang Ylang (10 minute walk down the beach from town). Another recommendation for a special romantic meal/evening is the Anamaya resort - it is definitely a taxi ride, it's way up the hill, but has the best view around and a lovely setting for it's bar/restaurant
I hope this helps - let me know if you have more questions or want more details on anything
There quite a few more too