Well, I don't think the acid will etch the concrete under any droplets of latex paint, but that's not going to make the difference between a good job and a lousy one.
If it was me, I would just use some acetone to remove the latex paint. Acetone is very volatile and will evaporate completely without leaving a residue within a minute. Acetone dissolves the acrylic and vinyl acrylic plastics that are used to make latex paints.
Alternatively, just take a paint scraper and scrape the latex paint off the concrete and vaccuum up.
But, in my humble opinion, what's vastly more important is to ENSURE that there's no water migrating up through your concrete. You can check a few spots on your garage floor with the aid of a hygrometer (which measures relative humidity) and which you can buy at Lee Valley or any hobby shop where people buy weather stations. Cut open a clear plastic bag and set it down on the concrete, slide the hygrometer under the plastic (dial side up) and tape the perimeter of the plastic down. If there's water coming up through the concrete, then the relative humidity of the air under the plastic will rise, and you'll see a corresponding movement of the hygrometer needle under the plastic.
Obviously, it's best to do this kind of checking in as many places as possible (or use a single large sheet of plastic and check the whole slab) during the wettest season in your climate zone.
If here's water migrating up through the slab and evaporating from it's surface, it'll push any paint off, including epoxy floor paint.
