We stayed at the Pura Vida Hotel. This was a few years ago. Berni and Nhi, the owners and hosts, lived on the property. There are several casitas to choose from in a small walled garden setting. At the time, some were more newly renovated than others. We stayed in a newer one (don't recall it's name) on arrival and an older one (Mariposa) on our last night there.
The newer one was larger (two bedroom with living area and kitchen) and better appointed. The older one also had two bedrooms but was much smaller (each just big enough for the bed, smaller older showers with inline water heaters, etc.). Both were clean but we did have some small ants one of the nights - I think not uncommon in Costa Rica. They serve breakfast on a garden terrace each morning, with fresh fruits, etc., which was nice. Nhi also prepares a dinner each night which you need to order earlier in the day so they'll know how many to cook for. The dinners were very good and the atmosphere pleasant. Berni was quite helpful making arrangements for drivers and the rafting trip we took, and drove us to the pickup point for the rafting trip quite early that morning. A driver met us at the airport (I think that was included in the room rate), which was welcome given the onslaught of free lance cabbies awaiting as you exit the terminal. There is no pool or other in-house activity areas of consequence - just a nice garden, meals and helpful hosts.
Our time there was short and pretty full of planned activites, so we didn't go out into the neighborhood at all. From what we saw coming and going there didn't appear to be much of interest in the immediate vicinity (i.e to go out and walk around a bit), but then again we didn't really check it out. We did some local car touring with Sterling, a driver/guide that Berni arranged. He was friendly and seemed to enjoy helping with my Spanish (and vice versa with some peculiarites of English). From some recent online reviews, it looks like he's still driving in the area.
I think they also may have a couple of rooms in the main house which might be nice for a couple, but I didn't see them. We were a family of four so the casitas worked better for us.
I also just noticed that my prior post mentions Tabacon as a potential day trip from Arenal. I meant to say day trip from Alajuela (perhaps a long one - but Tabacon is in the Arenal area). I no longer seem to be able to edit that post.
Edited to add: Re-reading some online reviews reminded me of a couple of things. In town Alajeula was kind of third-world noisy (e.g scooters zipping about, dogs barking, etc.) - Pura Vida neighborhood included. I *think* Orchideas is a bit further out in a more rural area and seemed like more of a hotel than Pura Vida. Orchideas also had a tour company working out of its lobby as I recall (we didn't stay there but used a driver based from there), so they probably could arrange any of that. If you're looking for all-hours reception desk, ever present staff or similar amenites of an American style hotel, Pura Vida wouldn't be that. But it was quaint and fine for us for a couple of nights' home base around a long day trip out, decent breakfasts, nice dinners and for sleeping (albeit with earplugs) not too far from the airport on our last night. Check the online reviews.
Have a good trip.
