Andorra la Vella is not a bad location if you want to go skiing because you can get either the local bus or the "Snow" bus up to most of the ski resorts. Most hotels during the ski season should have details.
The old town is worth visiting. It is up on the hill to the West and South of the main modern part of the town. It is quite old and quaint. You should cover it in about 2 or 3 hours.