I stayed at the Sea Horse while working near San Clemente for two months and I've been back for subsequent shorter trips. I have my wife and our baby with me on these trips and the Sea Horse and Villa Del Mar (down the street, owned and operated by the same people) have been great for us.
The location is perfect for my wife while I'm at work because she can walk the stroller up to the great shops and restaurants on Del Mar or to the beach and pier. The view is wonderful and we never closed our windows because the weather is almost always perfect.
The service is excellent. The manager and his staff are all very accommodating and willing to go the extra mile to make sure that you are comfortable and happy with your stay. They understand that this is not a brand new Marriott and sometimes people expect more than they can provide, but whenever possible they are very graciously helpful.
The price was comparable to the brand new Residence Inn where most of my crew stays.
The negatives are that these buildings are pretty old. The kitchens are not very modern and the bathrooms are old and don't have exhaust fans. They do have HDTV in most of the rooms, so my wife could watch Real Housewives while the baby was asleep and I had my ESPN. Do not expect luxury accommodations. This is a beach-side bungalow, not a five star resort. Also, the train comes through and can wake you up at night if you're a light sleeper. It woke my wife, but not me or the baby. They have fans available for white noise if you need it.
I'm staying there again right now and I'll stay there every time I come here as long as it's not their peak season and they're full. I can't say enough for the quality of the staff. They really make the place a pleasure to stay.