The closest and most convenient airport to Pasadena is Bob Hope Airport in Burbank (BUR); the next is Los Angeles (LAX); and other options include Long Beach (LGB), Orange County (SNA), and Ontario (ONT), each about an hour’s drive away.
From BUR to Pasadena, the Super Shuttle costs $23 and is bookable online: (http://www.supershuttle.com/).
From LAX to Pasadena, the Super Shuttle costs $25 and is bookable online: (http://www.supershuttle.com/). The best public transportation is to take the Flyaway Bus (http://www.lawa.org/welcome_lax.aspx?id=292) for $7 to Union Station in Los Angeles, then take the Gold Line light rail to the Memorial Park station, and walk the remaining half-mile to the Westin. A cab from LAX to Pasadena costs about $80.