bluecheeze-
The OC market is still pretty hot in that price segment. If you haven't gotten a solid offer yet, it means you might be priced too high or you (your agent) might not be marketing it properly. It's rare for anything priced around $500k to be on the market longer than 30 days unless something about the pricing/marketing is wrong. Why would a house with less upgrades than yours sell for more than your highest offer after 6 months? Something doesn't add up.
I also think your cashflow assumptions are probably wrong. It seems like you are expecting very little maintenance because the property is newer, but tenants are typically harder on a property than owner-occupants, so boost your maintenance assumption. Also, you either have an HOA, or a gardener expense, or both that need to be accounted for, but I don't think you are. Based on everything I've read, this doesn't make sense as a cashflow investment, only as a speculation on future price appreciation. Nobody can tell you if that will happen, but you've already said prices have dropped since these units were new, and now you can't get an offer that you think is justified (indicative of a weaker market).
There are literally hundreds of entities in Orange County that can manage properties, from large companies to individual realtors. I can't recommend any of them because I self-manage. I will tell you that from what I've seen, the larger companies will not give good service to a small guy like yourself. One property is nothing to them. I've seen rentals sit vacant month after month because often times the only marketing is a small sign in front and an obscure listing on their company website. The intitial vacancy with a large property manager might be longer than you expect and kill any prospects of cashflow, if indeed, there are any to begin with.