Plecos are beautiful fish (all a matter of perspective, though, my ex-husband thought they were hideous...), but you need to be sure that the one you pick is going to work for the job you need it to do and the size of your tank. Common plecos are really easy to find, but they get really big, and get a little lazy about algae after they get to be 8 or 9 inches. They'd rather eat the slime coat off of a slow-moving fish...
Other plecos are smaller, but prefer not to eat algae at all, such as the Q. Arabesque and the Clown. They are primarily carnivores, whose favorite snack is shrimp pellets (or better yet, shrimp...). There are some good pleco species out there that do the algae thing AND don't get to be big enough to eat your leg... such as bristlenose. This might be the best overall choice (if you are wanting them for a cleaning crew, otherwise, there are more colorful breeds out there if you're just wanting an "ooooh, pretty..." effect...)
My suggestion on tankmates would be larger tetra breeds, such as silver dollars, hatchetfish, etc., since you already know your water is well suited to tetras. The characin family is widely varied, and everything from neons to freshwater barracuda are represented.... (piranah as well, but they're not so peaceful...)
P.S. ALL plecos are poop cannons....