Bob, the main reason you see so little written about that area is that Mexico's Gulf Coast
offers little to the cruising sailor and it's East Coast
I did find a cruising guide covering the entire Mexican/American gulf coast
(which I gave to friends some years ago), so keep looking for that. There is an annual cruising/racing regatta
that goes down to Veracruz each year and the sponsoring YCs will have information you might find helpful...altho' in reading the guide, I found even that stop to be marginal in most respects.
The Tampa Bay/Isla Mujeres race
is conducted each year and, again, the sponsoring authority will offer some Gulf weather
and routing strategy info that, to some extent, could apply to you. Calder's NW Caribbean guide is now dated but his discussion of the Gulf weather
systems is timeless and, I thought, pretty good. The cruising S of Isla Mujeres is almost non-existant due to the short coastline and few anchorages
FWIW my advice
would be to not put much effort into that stretch of the C American E coast as there's much better, more interesting cruising further S.