As Steve said, the road is very rough. Patience is necessary and high clearance is highly advised. The route that we use goes up the ridge from the hillside cemetaries that are located southwest of San Antonio and north-northwest of Ortiz. Then you make your way southwestly to Lava. That's the stretch that is tough going. Best to have two vehicles in case you run into trouble. Good luck.
p.s. news reports seem to indicate that continued disagreement among the folks in Santa Fe indicate it's time to write the obit for the New Mexico annual "capital outlay" bill that was to have included projects funding for the C&T, along with many other entities. So I wouldn't expect any major work to be done at/on Lava Tank until some time down the road.