There are lots of answers to this question, but we need to understand what your purpose is. Are you looking to buy a lot in Alamo Heights on which to build or acerage in the country for a home? Small in price or size and a lot of that is relative to the use, zoning and other restrictions.
I like the fact you are thinking out of the box, but help me with this.
You can search MLS for San Antonio and New Braunfels on my website, including acreage.