I did a day’s biking with Lavatrax back in January. Hire bike was a fairly decent Marin hardtail. We did a route towards the north of the island (La Esperanza) which was up in the mountains and had some great singletrack, plus a fair bit of climbing.
I would have liked a longer day out as I’m a pretty fit rider, and this route was only 26k. (I’d happily ride 60+ in a day, 26k is a midweek evening ride). But the ride was good, and Darran the owner is a nice guy, he did try to find me a longer ride, but all the other people wanting rides that week were looking at shorter rides so it just wasn’t going to work out.
It was nice to see the other end of the island, which was very different from the barren south, think proper woods with slippy clay soil, great fun for riding. although there are also routes which stay out in the Sun and are rocky and technical I believe.
You can just hire a bike from Biking El Medano, which is about 10 miles or so from Los Christianos etc (buses are available) and go and explore, which with hindsight is what I would probably do. (El Medano is a great little place, so you could get a hire car and drop the missus there for the day while you go and explore)