You'll be missing the beach.
When we were in Arenal, we stayed at the Volcano Lodge. Nice place; great patio view of the Volcano.
Be sure to visit the Tabacon Hot Springs while there. You may also want to stay at the hotel located at Tabacon. I understand it is nice.
As far as chica availability.....I don't think there is any. You may want to check out a neat discoteque located several miles from Volcano Lodge. Seemed like hundreds of the locals were in attendance, but they seemed oblivious to our being there.
Zebra