It will be quicker to wait for the tax authorities to seize the property or find the heirs and make an offer. Adverse possession is a long process with subtleties that vary from state to state.
Agreed. Much better to get it through the tax process than trying adverse possession. State laws vary, but generally it takes from 7 to 20 years or so to gain possession and you have to physically take possession of that property for that period of time. Hard to do with vacant land unless you plan on living in a tent for 20 years!