A wee walk report I did after spending a day above the Amalfi coast
https://www.walkhighlands.co.uk/Forum/viewtopic.php?f=16&t=64102
In particular, the tracks on the hillside above Bomerano (leading down from Colle Garofalo) had definitely been used by the local DH brigade, fast loose and rocky, looked awesome fun. This would lead on to the Sentiero degli Dei which is a famous hiking trail (Path of the Gods). It’s stunning, and I think there’s probably some excellent riding to be had on it although not 100% rideable and finishes with a crazy long set of steep steps 8)
The hiking trails in the region are awesome, probably as they’re used by people still working the land, and I’m sure you could get into some mountains form Sorrento. Just be aware they build a lot of steps so you’ll inevitably end up riding steps.
I’d be almost inclined to suggest taking a road bike instead (tag on Vesuvius for bragging rights) and just enjoy the beautiful hiking, the hop-on hop-off buses are great for linking together A-B hikes.