CSUs with mechanical engineering include:
San Luis Obispo
Pomona
Chico
Fresno
Fullerton
Long Beach
Los Angeles
Northridge
Sacramento
San Diego
San Francisco
San Jose
While none are 100% certain safeties due to some level of impaction at all of them, if you apply to several of them (beyond San Luis Obispo, San Diego, and perhaps San Jose), it is hard to see you getting shut out of them.
Of course, another safety option in California is to start at a community college, do well, and transfer to a UC or CSU. This is obviously contingent on doing well enough to transfer (although Northridge is currently not impacted at the campus level for transfers, and not impacted for mechanical engineering, so just a 2.0 GPA will gain transfer admission as a California resident with the necessary course work).
Your 3.98 HS GPA and 26 ACT will give you a full ride to Prairie View A&M:
http://www.pvamu.edu/faid/types-of-aid-2/scholarships/university-scholarships/