I dunno, your very first bike trip and you choose Mexico?
plus as the others have rightly mentioned, you're most likely going to get your ass kicked by heat--and this is nothing to sneeze at, especially if you haven't ever toured before.
Of course it's doable, and maybe you are very experienced riding in hot weather, and talvez you speak Spanish very well also, but to an outsider joe blow on the internets, this seems a bit ambitious.
pero no somos tu madre, entonces haces que quieres, not sure how you will deal with the border restrictions.