I'd agree with 2F/2F that Old Pasadena, as appealing as it may be for shoppers, is not that distinctive. You can probably snap people outside the Cheesecake Factory wherever you are without making the trip to Pasadena. However, I have had the thought that all the empty storefronts that have popped up over the past two years in such an upscale area might make for interesting shooting.
The areas of Pasadena away from the "strip" of Old Pasadena may be a little more interesting, for example the area of Colorado Blvd. east of Pasadena City College (a little more "local" in flavor, and businesses that have been there for decades), or the streets that parallel Colorado, such as Green or Walnut. Not as much foot traffic, though.
The 3rd and Fairfax Farmer's Market has been done to death, but I was at the local farmer's market in Pasadena this morning, and lamented I hadn't brought my camera--the local markets always draw some characters, and if you're into shooting photos of food, needless to say there's a cornucopia of subjects.