Robert L. Riffle's The Tropical Look: an Encyclopedia of Dramatic Landscape Plants is a brilliant and readable introduction, and does not require anything resembling true tropical conditions to pull off, fortunate considering your location.

From Sunset:

ZONE 18. Hilltops and Valley Floors of Interior Southern California
Growing season: mid-Mar. through late Nov. Summers are hot and dry; rain comes in winter, when lows reach 28 degrees to 10 degrees F/-2 degrees to -12 degrees C. Plants from the Mediterranean and Near Eastern regions thrive here.

Rather than a tropical themed garden, I'd suggest you consider a waterwise garden. Most areas of SoCal are experiencing an extended drought (yeah, I know -- hard to imagine after this winter's rains!) and local municipalities and garden centers are encouraging homeowners to develop and install waterwise gardens, often offering rebates on plants to do so. A waterwise garden can be just as lush and colorful as one that is more tropical in feel - it is just a matter of careful plant selection.

If you are unfamiliar with the plants or gardening in general, a landscape designer or consultant may be a very smart investment. Fortunately, these are not at all hard to come by in CA! Have you asked for any referrals from your local garden center? Often they can provide names of local designers they are familiar with or they might even provide design services themselves.

The Sunset Western Garden Book is one of the best all around basic references for anywhere on the west coast. Every book store, garden center and Costco carries it.

Thank you so much! Your suggestions were very helpful. Im so glad the waterwise garden was mentioned as that is exactly what i was searching for. Im looking forward to the research in the books and hopefully finding a designer.