We just returned from Costa Rica (and would love to return!). I think you're safe with no reservations in Monteverde or Arenal area. We stayed at the Hotel Fonda Vela in Monteverde and would highly recommend it both as a hotel, for its dining room and for its proximity to the cloudforest. The staff is very helpful.

The roads are pretty astounding in the Monteverde area so we didn't do as much walking there as usual. It was just a few days past torrential rains; the roads are the walkways and were slick with mud. The cloud forest is a must (but you already knew that) and we enjoyed the hummingbirds at the Hummingbird Gallery. Unless you are quite savvy at spotting birds and other forest dwellers, hiring a guide is a good idea and fairly inexpensive. There are apparently other cloudforests in Costa Rica where you may see even more wildlife though they are less well known than Monteverde.

We would really recommend taking the 'jeep/boat/jeep' from Arenal to Monteverde (or the reverse) if weather permits. Apparently the road around the lake is in especially rutted condition due to the recent heavy rains. Other travellers reported lots of car sickness on the busses on the trip around the lake. The road from Monteverde to the lake is bumpy enough. We were there on an almost cloudless day and the lake trip was great. The boat only takes about 20 min. to cross the lake and I believe that it takes 2 hrs or so by bus.

In Arenal we stayed at Montana de Fuego hotel and it was quite nice but perhaps a bit more space than we needed. The volcano views are excellent from many hotels. They are building more hotels along the road from La Fortuna and spaces were available.

I'm sure that you will have a wonderful time! Patti in California