Sorry, I'm not much good on more recent records etc. If indeed Warren did go to Mexico, he may have been hiding, and there's the possibility he didn't even go by is legal name. Sounds like a real challenge.
You did say Warren left his wife prior to 1953, was there a divorce? If so, the courts had to make an effort to serve papers to Warren, maybe there's something in that record. I checked the online CA Dth Idx, which begins earlier (CA begins in 1940) then the one for TX. I put in Warren Wilkerson and this came up. You said Warren "went west" could this be Warren's son?
Wilkerson, Richard Warren, b 4-20-1955 CA; d 4-23-1955 Los Angeles Co, CA; 3 days old; mother Doubek; father Wilkerson.