Just in case, there are many nice guest houses beachfront at Shacks, but all you have at Shacks is beach (a great beach). I would stay there if you're going with a big group of people, in the mood for nice BBQs, beers and hanging out in the beach. Theres nothing else to do there, but a very nice hotel called Villa Montaña with 2 great (and expensive) restaurrants.. However, if you want to stay closer to night life, convenience store, restaurants, I would suggest staying at Jobos, in one of the guest houses or hotels such as www.oceanfrontpr.com/
. Jobos is the main tourist/surfing beach. 3 minute drive east of Shacks, and 3 minutes drive west of Montones. Montones is a favorite kiting spot for the locals. There's a very nice complex of Villas right in front of the spot. Beautiful place. If I were you, I would pick this one. Lots of friendly kiters. Google Villa Del Mar Hau.
As Danny said...you might want to rent a car, so you can move to other surfing spots, maybe visit the caves in arecibo on non wind days. Puerto Rico is a small island and you get a lot to see in short distances. For istance, you might want to drive 2.5 hours to El Yunque, our national Rainforest, which is considered one of the new wonders of the world (or something like that). You have the bioluminscent bays at Parguera and Fajardo, dry forest in guanica. the huge Observatory at Arecibo, etc.
Take in mind that the rideable wind directions in Isabela are East and North East. Any day that is South or South East, you might want to go to Parguera, which is flatwater heaven, 1 hour and 45 mins drive from Isabela. Contact there is Puerto Rico kite and paddle club - prkbc.com
As Danny mentioned, Pedro and the guys at kitesurfpr.com are also awesome resources. Antoine and Julie from kitesurfpr.com can hook you up for some very nice wave riding at San juan.
Hope this helps