I am thinking that the terms you want to go after are:
San Diego Mortage Loans
San Diego Mortgage
San Diego Loans
Since "San Diego Mortage Loans" is in your URL and is searched an estimated 3,000 times per month, I would start with that. Over time, you will rank well this term as well as variations of the term. Just because you focus on one, doesn't mean you won't rank for others.
For example, I have one site, http://www.ornamentshop.com, which I focused on ranking for "Personalized Christmas Ornaments". I am now in the top 2 in every search engine. Doing this made it so much easier to rank for "Christmas Ornaments", and not even trying, I am number 1 for "ornaments" as well.
In your link work, I would use all of the above as Google likes variations, if you just get links with the text "San Diego Mortage Loans", Google will see that it is artificial.
For content, you can use a nice little tool to see what Google thinks are synonyms of your keywords. Just add a ~ in front of a keyword. This will put any keyword Google thinks are synonyms in bold. Should be a thread I created about this tool.
It will take time for any sites you have to get good positioning. Google will take the longest. I always recommend submitting your site to DMOZ and the Yahoo Directory to help.
Let me know if you have any other questions.
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As far as jewelry, this is for my family's business. Something I did on the side. We also have http://www.TanzaniteJewelryDesigns.com and http://www.Moregems.com (being redesigned with over 1,000 products).