US64 is a good road, but it is a mountain road. From Eagles Nest to Taos, it is a bit curvy and slow. Between Tres Piedras (US285) and Tierra Amarilla (US84) there is a pass over 10,000ft. with a fairly steep descent on the west side. This section is closed some winters. But I would assume it is usually open by May. In May, I would not worry about snow sticking to the roads, but you would probably want to check the weather anyhow. If it is closed or snowy, you could take US285 south to US84 and then back north. US84 is a nice drive also.
David
