Though this street vendor sets up in the early morning, not far from the Fruitvale BART, it's not purely with breakfast in mind. Pre-made tortas were wrapped to go, and takeaway, I now believe, is also the intent for champurrado (about a pint, $1.50), the chocolate version of the cornmeal-based drinks called atoles. I started on mine immediately, despite the server's caution, but had to give it a rest; here it's served very, very hot.
Champurrado cart
Fruitvale Ave. between East 16th and East 17th Sts., Oakland
(From an August 2011 visit)