"Mexican heather" is the common name typically given to Cuphea hyssopifolia, a very tender evergreen with light purple flowers. It's not a heather at all and is typically sold as an annual (sometimes a houseplant) in climates colder than zone 9. There are red flowered forms of Cuphea as well - perhaps yours is one of these. These often go by the name of cigar plant or bat-faced cuphea. They can certainly be a hummingbird attractant, but chances of overwintering these plants in zone 7 are slim.

Did you ever figure out info. about your "mexican Heather"? I just bought what sounds like the same thing - and was labled the same too but I'm suspicious this is it's real name. Any info on it and care instructions - beautiful plant - I love it! Thanks.
lora

Mexican Heather is Cuphea hyssopifolia as Gardengal stated.

It is NOT heather in any way, shape or form.

It is a summer annual in all but frost free climates.