Tamrindo or Flamingo?
 

Does anyone care to comment on a preference as to set up as a base. We are also considering Manuel Antonio.

What kind of things do you want to see? That could help to give advice on where to base you. Tamarindo/Flamingo is a very different area than Manuel Antonio.

Hi There,
We have been in Tamarindo(7 days) last time we were there and had a ball. Flamingo is right up the road and went there to sail and golf. Both are very small towns(I mean walking fromone end to the other but thats what we were looking for. Flamingo has a great resort but not much else to do but golf. Its very pretty. We stayed at Hotel Pasatiempo(65.00) a night. Small bungalows around nice pool, resteraunt, bar and very nice people. 5 minutes to the beach. Quiet, pretty nice beach shops and just laid back fun. We loved it. Good Luck
Sandy

I am using Mmy frequent flyer miles and can only get into Liberia. We want to send some time re;axing at a villa, but would like to see the Volcanos and Monteverde. The maps make it look like it is possible to do long day trips from the NW coast. Do you think this is possible?

I think Tamarindo is a bit larger town than Flamingo - more restaurant choices, etc.
I believe you could possibly make Monteverde as a day trip from there if you leave early but Arenal would be a bit much. Distances in CR can be deceiving - the roads are not superhighways!
Depending on your time available, I would consider staying in 2 or 3 spots; don't miss Fortuna and the Arenal area!