I received my itinerary from my travel representative and they recommended that I wear long pants for most of my activities. I am interested in your opinion of optimal dress for the following activities:
1) Mountain Biking in Arenal long pants or short pants?
2) River Rafting in Sarapiqui bathing suit, t-shirt and old sneakers?
3) Hiking in Arenal Forest Long pants or short pants? Long sleeve shirt
4) Canopy/Sky Bridge in Montreverde Long pants or short pants? Long sleeve shirt
5) Hiking in Monteverde Reserve Long pants or short pants? Long sleeve shirt
6) Hiking in Manuel Antonio Park Long pants or short pants? Long sleeve shirt
7) Horseback riding in Manuel Antonio Long pants or short pants? Long sleeve shirt
8) Kayaking in Damas Estuary bathing suit, t-shirt and old sneakers?

When I wear long pants, I'll wear workout or sweats. (Got that idea from this group) Anyway, please give me your opinion of optimal dress. Thanks
I leave for Costa Rica in 2 weeks. WOOHOO!

On our trip to Arenal and Monteverde in January last year, I wore hiking shorts every day, then long pants in the evening when we went out to dinner.

It was cool in Monteverde, but I was fine as I was physically active the entire time. I layered my upper body--light short sleeve shirt, light long sleeve shirt, and a light waterproof jacket.

Wore waterproof, lightweight hiking boots to keep feet dry and provide good traction, and a fedora to top everything off and keep rain/mist off of my glasses and out of the back of my neck.

Basically, almost everywhere you go in CR it is warm and humid enough for shorts. The only exception would be the top of the tallest mountains. Long pants might be recommended for trail hiking in the bush and certainly horseback riding. You will want something light and breathable - cotton khakis maybe. Leave the sweats and levis at home. Sounds like a fun trip you have planned. Good luck and have fun!

I think the rationale for long pants is to avoid insect bites. Would heavy deet be enough to avoid the mosquitos, sand fleas, and bullet ants or do I need long pants?

Nix the "old sneakers" plan for rafting/kayaking. You'll just have soaked sneakers to deal with. And don't throw out old clothes as a bad gift to CR.
Ideal: water shoes.. or tevas, columbia or quality sandals ... or cheap beach sandals .. I'd go barefoot risking stepping on sharp rocks, before i'd wear sneakers.

When horseback riding in Costa Rica, I wear shorts, but take a beach towel. I throw the beach towel over the saddle to protect my legs from saddle burns, etc...and the towel comes in handy as often tours stop at waterfalls!

We just got back and wore the nylon-type zip-offs pants everyday. If we got too warm, we wore them as shorts. These are great, too, because they dry quickly. Sweats would never dry! In Manuel Antonio, it was way too hot for long pants! We used 30% DEET with good results, my kids got a few bites, but I think it was when we forgot to use the spray. As for shoes, we wore hiking boots for hiking, tennis shoes for general walking around and Teva sandles when we were near the water - the tevas were actually fine for hiking in MA, however, we did wear socks with them and that worked well because of the stones on the trial. Then we were ready for the beach after the hike. Have a great time!

Ally - I read where you posted this towel idea before. I was wondering - Does that towel not slide in the saddle?

I hated wearing jeans when we rode - they were so hot. Obviously I had never considered your suggestion.

dariow - yes the idea behind long pants is sometimes to protect from insect bites, as well as scrapes and sometimes too much sun and for warmth in some areas.

The lightweight zipoff pants give you two for one. Start the day in cooler climates in pants, once the day warms up you can easily zip off and store the legs.

Arenal should be warm enough during the day, can cool off at night, needing a long sleeve or lightweight wind or rain jacket and long pants if hiking at night.

Monteverde is your coolest destination, and can get quite cool in the evenings. High winds and mountains. We did wear long pants while hiking, here.

MA is going to be hot!

As already suggested a hat - we tend to wear a ball cap under our hood, to keep water from dripping down our face.

Shoes, as already suggested, ditch the sneakers. You need a shoe that is designed to get wet, drain water and give good traction. We also wore boots for hiking both Arenal and Monteverde.

We fortunately have never run into a big insect problem. However insect repellent - Yes - much more comfortable than hot long pants.

No, never had a problem with the towels sliding in the saddle. I'm a fairly 'decent' rider so my butt stays pretty much in the saddle, so no towel sliding!

I can only answer #6 from experience: definitely shorts.

And I wouldn't bring sweats at all--only lightweight pants. Sweats would never dry and may be too hot anywhere in CR. Have a great trip!

I wore sweats and was worried about the heat. It rained about 10 inches so the long pants worked at great. Fantastic ride also.