Danube cycle trail notes.
Budapest to Esztergom: we followed the west side of the river to the ferry, crossed to Vac, then recrossed at Szob. Stayed at Esztergom, campsite. This was all good, nice scenery, though surfaces often bumpy, little traffic. few signs. Recommended

Esztergom via Komarom to Gyor not so nice. Mainly on traffic busy roads, no view of Danube. Gyor is a huge industrial city, difficult to find way in ( little signage) but we loved City Camping. Maybe try north of the river instead?

Gyor to Bratislava. We left to reach Slovakia at Medvedov, then on long traffic free dykes with good surfaces. Good views of river, but its a bit all the same. Pray for dry weather & no head wind ( we got a stinker). No signs at all in slovenia. Bratislava easy to access, good place. Do the walk tour.

Then you reach Austria where of course all is perfect! We crossed the river and left the Danube after Hainburg, going north.