in sosua, it depends on which beach guy you go to, but most are around 100 pesos for a chair, and 150 pesos for an umbrella.
or, at least, that is what jesus charges. he can be found in front of Big D's bbq, stall #109B.
or further down towards charamico's is a bar/restaurant called the black box. if you are a patron of his, then chairs and umbrella are free.
Ad is the owner (pronounced Odd) a very nice guy.
i do not have experience with other beach chair vendors so im not positive of thier prices. and im not sure if other restaurants offer free beach chairs like the black box does.
can't help ya on cabarette, sorry.
there are no lockers to be rented in sosua. only take what you need for the beach. and while there certainly are occasions where something might be stolen.... it is rare, imo, during the day at sosua beach.
they are pretty much self policed. ie: the vendor you are renting the chair from. they keep an eye on thier area, because if things get stolen from thier area, word of mouth would quickly diminish thier business. or they would get booted and replaced.
i've been to sosua beach 7 times. i spend all day every day at the beach. i usually have my ipod, my camera, my phone, my wallet, and my towel. when i go swimming all these things are left on my table. they are not in plain sight, they are covered with my towel, but they are still there.
occasionaly, we get up and go for a walk up and down the beach, or we go to lunch at one of the restaurants.. in those cases, i take my wallet, camera, and phone. but usually my ipod gets left behind, along with my towel, and whatever my traveling buddy has. we've been off wandering sometimes for 2 hours before returning to our things..
have never had an issue.
didsclaimer: of course, im not saying that it NEVER happens... but i do not know of anyone PERSONALLY that has had anything stolen at sosua beach.