Hi Myles,
Great to hear about your upcoming trip… and your desire to learn to surf. I’ve been learning to surf for a couple of years now. My seven year old is much much better. 🙂
As far as destinations, you might check out Jaco or Tamarindo. Both are developed beach resorts with nice restaurants, nightlife, etc. Also good surf for beginners and good and plentiful surf schools. But keep in mind that the Xmas to New Years period is the time when all Costa Ricans go on vacation. Add in foreign travelers and you’ll find both area, any beach areas in the country, very crowded. So make your hotel reservations ASAP.