While "world-otmu" has said may be true, When a Mexican says, "¿Mande? it's just the polite way that Mexicans use to way, "What", "I beg your pardon" and things of this nature.
I am Spanish (from Rota, near Cádiz) and never heard "mande" used as Mexicans use it. One just has to accept it as a regionalism at this point. Mexicans do not feel inferior when employing this word. As I live among Mexicans and as my late husband was Mexican, I use it all the time myself.
Just because the expression has "humble" origins doesn't mean you degrade yourself when using it.
"Ojalá" comes from an Arabic expression "May Allah grant" or something of that order.
I don't feel that I'm praying to Allah when I use that expression. It has found its way into the Spanish language as meaning "I hope," "I wish" or similar expressions. That's all!