We stayed at Club Del Sol for two nights during early August (rainy season) so no huge crowds. In fact, there weren't too many other folks there at the condominiums. The rooms were beautiful, the grounds lovely, and the office staff pleasant. Our kitchen was equipped with the basics, so we could cook, make coffee, wash dishes, etc. and we had our own laundry room. There was always a security guard at the parking lot, and the gate to the lot was closed at night so we never worried about the car.
The only thing we'd do differently is bring our own coffee and some food for the fridge. There was no complimentary coffee like you often see at other chain hotels and no restaurant within easy walking distance (it's a short drive to the main street in downtown Jaco, where there are restaurants, souvenir shops, and a grocery store.)
All in all, Club Del Sol was the perfect base for the beach/zipline/national park tours portion of our Costa Rica visit. If we ever make it to Jaco again, this is most probably where we'll stay.