Aside from the Multiple LIsting Service which is accessed by REALTORS, you can use the following as possible sites: craigslist, backpage, trulia, zillow, signonsandiego. Please use caution though as, unfortunately, there are a bunch of rental scams out there. While you can certainly go about this on your own, it wouldn't hurt to enroll the services of a professional who can network and may be aware of possible rentals that aren't actively on the market. The rental market is hot, with vacancies at very low levels, so you will want to act quickly if something comes up meeting your parameters. Best of luck!
By the way, great idea to be a part of the Poway Unified School District and that is coming from someone who went through from elementary to high school and found the entire experience to be very rewarding!
Chad Basinger, REALTOR, CPA, CFP