i have an angel in my 29, along with 2 mollies and 2 dwarf gouramis, and i like the look of it, everybody is doing their own thing, no schooling.
Yes one angel is generally the max, but if you get a breeding pair(which is hard to find) they should get along, but they may fight occasionally. One angel should be in at least a 20 gallon, with 10 gallons to himself. Remember angels are cichlids, not just nice and pretty fish, they are vicous. So basically only one for your setup.
AS for fish, i would ditch the plecostumus, because chances are its a common pleco, and those get to at least 18 inches. You could get some schooling fish like some larger tetras, such as bleeding hearts or skirt tetras, but make sure you dont get tiger barbs, as they will terrorize your angels fins. Or go with the setup like i have. Which ever your choice, i wish you good luck!