I second Dana Wharf out of Dana Point. Had a great experience and actually went out twice during the week for the price of one trip. Our first time we did not see any whales but did see tons of dolphins, seals and other marine life. They gave us a free 2nd trip since we didn't see whales the first.
There are several discounts available online. Use code NETT40 for 40% off or on Tuesdays they are always 1/2 price. Groupon sometimes has 1/2 price available as well.