Hi Mike
Depending on how frequently you want to do the steam cleaning will affect what you should consider. If the floor is already clean, then a steamer for ongoing regular maintenance is fine. If the floor & grout is dirty, you could rent one from Rental Yard or Home Depot.
They are not necessarily the quickest or effective way to get the job done.
I have done jobs that the homeowner gave up on using their steamer, because their patience wore out.
I have great success using a tile and grout specific high alkaline cleaners on heavily soiled tile and grout.
Could you post a picture, and state how many square feet you have to clean/maintain?