Okay let me make this one post as long as I can just to throw out all the info I can remember without digging through all my papers...
Costa Rica is a very safe place to visit. All the locals encourage tourism because they all depend on you spending your $$ in the country. Another thing to note is there are a lot of Americans who own enormous ranches (they also own a lot of tour companies) so its easy to find friends down there. I never ONCE felt in danger or unsafe, and I was out and about for 10 days in the middle of no where at times.
I changed bikes depending on what part of the country I was in, I first got to Arenal (by the volcano) and in that area it was dirt bikes, and ATV's because there is so much gravel in the area, you can go solo, or with a guided group which I did in the first city. After leaving that city and heading towards MonteVerde, by luck our driver was a local motocross champ, so he took a detour and showed us the track that is used all year for the competitions, I thought I was very lucky because he was able to direct me to a many bike rental companies.
http://www.wild-rider.com/contact/
http://www.costaricantrails.com/adventur/moto/moto00.html
http://www.costaricamotorcycletours.com/
I would put more but I have to sift through all the brochures I brought back with me... some tour companies will wink out of existence, only to come back later with a different owner, not sure why, don't really care. They do make you sign a waiver no big deal.. I had to sign them for all the "crazy" activities I did..
As for the road conditions, they are excellent. Where there are real roads, they are in perfect shape and feel like they were just paved. The Pan-American highway I noticed was very busy with riders lots of SS bikes, and also a handful of touring bikes with extra tires (they may have gone up the mountains which have no paving and when I say up the mountain, I mean WAY up with a one lane road with no barriers).
I would say 90% of the roads I saw (and i did a huge loop of the country over a 10 day span) Nothing I rode was worse than for example Steeles Ave around Younge st. And that's bad, but once you pass through the major cities (not even as large as Richmond Hill) these cities are tiny... like a very small town... the roads are smooth, and very curvy. So the roads get a huge thumbs up from me, as for traffic, if you are on a good bike it wouldn't even be a problem because its so sparse (and I was down there during their peak holiday times). The drivers help each other know when traffic ahead is clear so you can pass trucks and slower cars.
Another thing to note is cops.. and speeding. They are much nicer down there when it comes to speeding. I asked a local how much does a speeding ticket cost and how often does it happen. The motocross driver told me $200 is the max for 50 over.. I just started laughing.. so nothing scary there. Do it if you feel like it, but don't go overboard, because often you cannot see beyond the next right..
Bikes available : Any range of Honda and Yamaha 50- 400 cc dirt bikes, KTM touring bikes, Yzf, older gsxr's 2001-2005, it just depends on what you book ahead of time, and where in the country you are heading.
I will FOR SURE be going back there, except this time I want to do what the Motocross guy (I can remember his name for the life of me) told me to do, which is take the pan american highway and head south to panama, or north to Nicaragua and enjoy all the roads in those countries. apparently a lot of americans do the touring thing through central and south america. Just don't go deep into the forests in Nic and the rebels wont bother you.
If anyone is looking to go, I can dig into my papers for the real details and PM you..
