If you are just casual riders --as opposed to long distance riders-- either bike would probably be fine. I'm a little familiar with Burley and think they make a pretty good product. One of my other bikes is a KHS (not a tandem) and is well made. These bikes won't be as light as a SANTANA but then they are a third of the cost. Be sure the bike fits you both. Any bike shop should be able to set it up so the stoker is comfortable.
Finding used is a matter of hunting in newspapers, bulletin boards, yard sales etc. And word of mouth. Let it be known that you are looking.
Welcome to the forums. You'll find some more tandem riders here as well as just everyday riders. Alot of good people who will be more than willing to give advise and encouragement.
Huntington Beach, isn't that just south of Long Beach?