We are a family of 5 adults visiting CR for the first time in late May. We fly into SJ at noon. We will rent a car and drive to an undetermined hotel/B&B maybe near the Poaz Volcano. The next morning after touring/visiting/hiking the Poaz area, we plan to drive to La Fortuna.
What is the best route for that time of year? Go North on 140 to 250 to 4, or go back to Alajuela and head over to the Pan Amer. Highway? How long will each of these routes take? Thanks in advance for your help!

First, I'd like to recommend Poas Lodge; funky place, very good value, absolutely awesome views very close to the park, and very good food. http://www.tripadvisor.com/Hotel_Rev..._Alajuela.html

The highway through San Miguel (going past the Peace Lodge) to 140 and then 4 is open and a fairly pleasant, easy drive. EXCEPT that 4 km of road (that was closed before) is pretty rough. However, you drive by a gorgeous waterfall, and see them in the distance, so it's rewarding.
So, leaving Poasito, near and after you pass La Paz/Peace Lodge, there's some rough road; then down the mountain for 15 minutes to San Miquel; then follow signs to Aguas Zarcas, Muelle, to La Fortuna. (We did this in February.)

Here are directions (in reverse, Arenal to La Paz (keep going to/from Poas) that are helpful: http://www.waterfallgardens.com/map_directions.php

Thank you so much. The Poas Lodge is booked, but what a good recommendation.
Your directions and input have helped greatly. Now I can go forward with planning the remaining trip. I was worried that the roads would be impassable. Can you tell me how long the trip would take?

The trip was fairly fast, as I recall, about 2 1/5 hours from La Fortuna to Poas; BUT a huge chunk of that was taken up by the drive over the rough road. (We left Fortuna at 9 a.m., got to the volcano before noon, as I recall.) Although we saw a couple of sedans on that rough stretch, I wouldn't recommend driving anything but a 4 WD (and DH says it seemed longer than the "4 km" on the La Paz site).

A couple of notes; earlier the better for a view of the caldera (a walk from the parking lot of ~10 minutes). And, if it is totally obscured by rolling mists, etc., give it 10 or 15 minutes, if you can. We saw people walk away because they couldn't see anything, but our patience was rewarded.

Don't mean to steer you away from going through Grecia and Sarchi; it you haven't driven that route, it is also pretty. (Just tricky when you get to Alajuela.)

Thank you! Yes, we plan to spend up to two hours at Poas. I will have to drag my 21 year old son out of bed to be there at 8 am, but I know he will thank me later. I thought I read somewhere that there are good hiking trails there too. Correct?

There's also a lake you can hike to. We had the same experience - arrived to find Poas covered in fog, but it lifted eventually, and we got a great clear view. The crowd actually cheered!

The lake trail is less than 2 miles round trip, I think; there's also a birding trail that's a bit shorter. Bring a windbreaker, it can be breezy and chilly!

Don't rent from renta4x4incostarica.com - we did in Dec 2010 and got a broken down vehicle that we were sure would never make it back from La Fortuna. The 4x4 wouldn't stay in gear, leaked oil, the air conditioning and defroster didn't work and the windows wouldn't go down. We drove several miles with both front doors open so we wouldn't pass out from the heat. Owner never responded or compensated us in any way.

we just got back from Costa Rica. Poas Volcano Lodge was place we stayed. Main Lodge & that area very nice. Rooms were extremely rustic. Fine if that is what you are expecting (no phone, TV, closet, etc) No heat, and nights go as low as 38 degrees. They have a restaurant but we wer surprised they only offered a fixed price dinner for $30.75 per person. Next nearest place to eat would be a significant ride away. Did have great views, but not of the volcano, just the valley.

Hmmm...we had a giant king bed, bathroom, fabulous views, heater, and satellite tv in our room.
The menu had all kinds of entrees, including very low-priced offerings, like tortilla pizza with fresh mozzarella and herbs. The $75 rate included tax and breakfast. Looking at their website, it seems all the rooms have tv:
http://www.poaslodge.com/Accommodation/
But, it's a moot point, as they are booked solid for the OP's dates.

Oops; that's newly renovated Poas Volcano Lodge you are referring to, not Poas Lodge (about 1/4 mile apart, so not too far if you want to eat at Poas Lodge instead of Volcano Lodge).
Sorry for the misunderstanding.