Shore fishing on the Pacific coast of CR is a crapshoot at best. I've heard that there are more Roosters around Quepos than in other areas, but more is still certainly not a lot. I've fished CR from shore on 4 separate trips, and I think I might've seen a rooster once. As for tarpon, you're on the wrong coast, and it'd be at least a day or hard driving to get there.
If the stars align, there can be jacks found on the beaches, but they really only show up when the anchovies drift in - if you hit it right it can be great, but most days it's dead.
The rivermouths and estuaries will hold snook (Robalo in Spanish) and they're probably your best bet, especially if you can get a canoe or kayak for the estuaries. Striper flies work fine - clousers, shrimp patterns, etc. The water is likely to be a bit tannic in the estuaries, so bright colors can work great.
If you have a travel rod, I'd say toss it in the bag - you'll be kicking yourself if you have to sit through a blitz, but don't be surprised if you never even string it up. I've been going to CR for a few years now, and I don't even bother fishing the Pacific coast anymore.
One final note- property crime is a HUGE problem in CR - don't leave anything in your rental car - ever; and get the extra insurance on the rental- chances are your stereo will get stolen. Violent crime is still relatively rare, so I don't worry about that outside a few hotspots (San Jose, Tamarindo), but if you take your eyes off of anything for more than a couple of seconds, expect it to disappear.