What you say during your ceremony has zero to do with the legality. The legal part is only this: you signing the papers with the minister or justice of the peace after the ceremony, with witnesses.
I wrote to my friend Robin Clements who does more kind of New Age ceremonies in Cabo and he said this:
"To do the legal part down here you need to arrange a judge and have your blood tested, I recommend couples to go to the Civil Registry where they are from (in the States) before the ceremony down here, although doing all the paperwork here adds a nice latin theme to the day and it is legal in the states."
When I shot a wedding with Robin at the Pedregal, he did a beautiful New Age ceremony, but a Justice of the Peace signed the papers afterward with the Bride and Groom.
Best to you!
Joel
Cabo Wedding Video