Spent many vacations there, but my last time was several years ago. Cigar shops weren't on my A list then, but tarpon fishing and the beaches (and women)were phenominal.
I found, even then, Cuban cigars were available but costly. Fakes were around but not like Mexico. Cubans are legal there of course, but tobacco taxes are high on imports. (all imports are taxed up the wazoo regardless of the product). You will get a feel for people who are being honest. A nice, well kept tobacco shop will probably have a genuine thing for sale. Liquoreras, bars, convenience stores, won't have the real thing for the most part.
You can get the best deals on the local stuff. Anything made there is sold at a good price. If you want to load up on what Costa Rica does best, stick to coffee and rum. (I used to bring an empty suitcase and fill it with coffee and rum, but that was before Customs really clamped down on those things). Buy your coffee and rum at a Supermercado not at a tourist shop or airport.
Always have your passport. Everyone will ask for it. cops are cool if you give them a few Colones (bucks) to watch your car or to give directions or advice.
Enjoy your trip...wish I was going again soon.
