I am intereted in key stopping points that shouldn't be missed on our drive from San Jose to Arenal. Also, on our return trip, any interesting sites on the drive from Manuel Antonio to San Jose.

I don't think there are any key "stopping points" along the way to Arenal. The views on your drive will be amazing in themselves. La Fortuna is a nice little town (on your way to Arenal) and it's very close to Arenal. Fun to walk around there.It's only minutes from Arenal so you can visit the town after getting into your place. Unless you are staying at Arenal Observatory, that' a bit of a drive away. If that's the case I would stop along the way. A great restaurant in Arenal is El Novillo. Little place on the side of the road with great food and great prices.
Driving from MA to San Jose, you may enjoy stopping in Quepos or Jaco.
WATCH OUT FOR THE POLICE NEAR QUEPOS
They stopped us and ripped us off $80.
Totally illegal, but they refused to return our passports and we were worried. Learned after that they can go to jail up to 10 yrs. for doing that. Don't give them any cash- insist on the ticket! Which you pay when returning your rental car. Take their names if they hassle you, better yet take a photo or video!! Seriously!

I would suggest a stop at Poas (early in the day before the clouds roll in), then perhaps a tour of the Doka Coffee Plantation and then a stop at LaPaz Waterfalls. These are all along the way to Arenal.

The most direct route to Arenal from SJO is through San Ramon and Poas/LaPaz will not be on that route. But I agree they would both be worthy stops should you choose a different route and get an EARLY start on the day. Need to be at Poas by 8:00 or 9:00 a.m. Have fun!

I posted something similar before my trip. We decided to stop at La Paz and hike to the waterfalls. But then I remembered all the warnings about NEVER leaving ANYTHING in your vehicle...of course, we would have had everything in our vehicle, so we just drove straight to Arenal.

We stopped at La Paz and thought it was well worth it. We wanted to go to Poas but it erupted the day before we got there and it was closed.

As for warnings about things in your car - if you leave them in the trunk or under the "protector" in an SUV, you will be fine. Just don't leave things visible. We did this in numerous places and had no problems whatsoever.

Have a great time!

Karen

If you're going through San Ramon, stop at Tierras Enamoradas and eat. The hotel is run by a group of 25 Israeilis, and they make the best vegetarian food ever. I'm a confirmed carnivore, but this place is worth a stop!