I think there's a Holiday Inn at MoPac and 183, which would be closer than the Arboretum. There is also some sort of executive suite hotel just south of Northcross Mall.
If you'll consider B&Bs, Citysearch says there are some that are very close:
1309 Meriden (Tarrytown)
Carriage House (West 22.5th St.)
Carrington's Bluff (1900 David St.)
Brava House (1108 Blanco St.)
Austin's Inn (Pearl St.)
Heathy Quarters (Lost Cyn)
Hardin House (2206 Rio Grande)
I've only heard of some of them, and I've stayed at none of them, so caveat emptor and all that.