Jason,
I've probably played this course two dozen times. It is short and tight, but it isn't like anything else you'll find in Tucson. There are mesquite trees lining just about every hole and plenty of great views of the surrounding mountains. Its not in the same league as a Omni Tucson National, but it is a personal favorite and offers a more authentic Tucson flavor.
Steve,
I've played Silverbell three times in the past three weeks. The conditioning is awful (really horrible), but the new layout is far superior to the old. The architect they brought in put some serious thought into the previously bland design. The opening hole is pretty interesting. It is a long par 4 (440 from the whites) with water down the left and a couple large bunkers which sit middle-rightish of a very, very wide fairway. A ton of options off the tee on the very first hole.
As for El Rio -- its the same old course with a couple more bunkers guarding tee shots which run through dog legs. I wouldn't bother with it and I live 10 minutes away.