I second Paraiso Quetzales - beautiful location and just off the Panamerican Highway. My husband and I traveled there a few years ago, we just took a bus from San Jose and had the driver drop us off at the entrance road. I think it was ~1km walk to the lodge from the road.
You might also consider Monteverde - you can get there using either public buses, or you can hire one of the more direct transport van services - I don't recall the names of the companies, but a bit of googling on how to get from San Jose to Monteverde should bring them up. Once there, there are a range of lodge and hotel options, many within easy walking distance of multiple reserves.
I've been to Costa Rica 5 times and never bothered with car hire - it's just so easy and cheap to get around using public transport, especially if you just want to station yourself at a single location for a week. Knowing a bit of Spanish certainly helps with navigating public buses but I bet it could be done without.