If they force you to gate check your bag, there will not be a bag fee charge. They do sometimes preemptively ask for gate checks and offer Main 1 boarding. If you get a Delta Amex, you also get Main 1 boarding, even with basic economy.
One note...you cannot gate check your laptop, as it has a lithium battery, which cannot go in the cargo hold.
All that said, I feel like Mexico is a route more people will be checking, so there is usually more overhead bin space.