It'll depend on weather. But Moab is fabulous at any time of year. Onion Creek is still one my favs. Tons of little water crossings make it particularly fun. I also would suggest Top of the World if the weather is good, no snow and pretty dry. There's a few tougher spots, but you can go around the hardest spots if you need to. Going alone on those previously mentioned trails is probably fine, but you can also find others to go with just by asking around. Biggest thing, just have a blast!