Genetic Genealogy

In talking with others who have looked into their genealogy, I've discovered that genetic genealogy is frequently overlooked.  Yesterday I had a conversation with the owner of a store that I frequent and he mentioned having hit a brick wall with his genealogy on his family name past his great-grandfather, who abandoned the family.  He knew the family line was either English or Irish, since permutations of it exist in both locations, but he didn't know which it was.
I asked him if he had thought of having his Y-DNA tested, and he indicated he didn't even know about that.  I explained to him how a Y-DNA would probably be able to tell him where his family came from, and possibly their migration patterns.

My own DNA tests have only come back in the last month and are already resulting in new information.  My patrilineal pedigree from my grandfather:

(3)  Ralph Gomez (b. 1917 Mexico d. 1989 Sacramento, CA)
(4)  Benjamin Gomez (b. 1895 Mexico d. ???)

I have a border crossing document from the family dated in 1922 stating that they last resided in Tepic, Nayarit, Mexico.  My uncles say that Ralph claimed that the family was from "a small town south of Mexico City."  Despite my searching so far, I have yet to find any records of the family in Mexico, so it's difficult to know where exactly they originated in Mexico.  All I know is that Ralph wasn't born in Tepic or the few cities I've had time to look through the documents from (or, at least, it's not reflected in the preserved documents).
The lack of information prompted me to order a Y-DNA37 test from Family Tree DNA, the results of which I've received.
Initially I was underwhelmed with the information I received.  Literally, if you're expecting your results to give you new information, you'll be disappointed.  About all I learned was that I was part of haplogroup J2, and that I was likely to be from J2a4b1 specifically because all of my genetic cousins were from this type.

However, I joined three research groups shortly after receiving my results:
J Haplogroup Project
Gomes Surname Project
Mexico DNA Project
Each of these projects has a different research focus for looking at the DNA of the members, so have provided different information.  I've learned the following facts so far:

• The Gomez name has wide-spread genetic origins (meaning multiple male origins, not all of which are haplogroup J2).  This was initially very confusing to me, until I learned the second item...
• Mexican culture has a long tradition of inheritance of the matrilineal name, especially in the colonial era.  Gomez was the last name of one of my female ancestors prior to it becoming a patrilineal name.
• Because of this matrilineal name inheritance, I share a common patrilineal ancestor some time back with families that have the surnames Ramirez, Soto, Gomez, and Gonzalez (these are just the ones that are known).
• The family appears to be primarily from southern Mexico and Central America.  All roads appear to lead back to Jalisco, Mexico as the source of the family.
• The genes are ultimately Semitic.

That's all I know so far, but it's waaaaaaaaaaaay more than I knew before, and is a reason to contact that Ramirez in my list of close matches (I initially wrote that connection off because he didn't share my family name).

And it's all within a month!