Caltech has agreements with these hotels and you can get special rates described here.
551 S Hill Ave,
Pasadena, CA (On campus)
626 395-8200
The Athenaeum
1633 E Colorado Blvd, Pasadena, CA (0.5 mile to campus)
(626) 795-0431
The Saga Motel
168 S Los Robles Ave, Pasadena, CA (0.8 miles to campus)
626-577-1000
The Hilton Pasadena
303E. Cordova St, Pasadena CA (1 mile to campus)
626-449-4000
The Sheraton
180 N Fair Oaks Ave, Pasadena, CA (2 miles to campus)
626-403-7600
The Courtyard
(formerly The Ritz Carlton)
1401 South Oak Knoll Ave., Pasadena, CA 91106 (2.5 miles to campus)
(626) 568-390
The Langham