Well - there's actually two species stingrays known - the Blue spotted Ray.
The most common species found in Home Aquaria is The Blue-spotted Ribbontail Ray (Taeniura lymma). This species grows to about 27.5" (about 70 cm), and known to have a very low survival rate in captivity. So even though it's a popular species, it's really not suited for home aquaria.
The second species - Bluespotted Stingray (Dasyatis kuhlii) is much rarer, and a total length of about 26" (67cm). But generally this species is consider to a much hardier species, that better suited for survival in captivity.
As for the Cortez Stingray (Urobatis maculatus) - is actually an excellent species for home aquaria. It's maximum length is about 16" (41 cm). It's one of the round rays like the California Round Ray, and the Yellow Stingray, both smaller than either. The general recommendation is the Cortez needs a tank that is at least 180 gallons (note - "Aquarium Sharks & Rays - by Scott W Michael). And is usually consider to be a fairly hardy species.
By the way - you should consider picking up a copy of that book - if you seriously considering getting a SW ray - lots of useful info for sharks & rays in home aquaria.