While Hop On Hop Off Rome (https://www.hop-on-hop-off-bus-tours.com/tour-city-sightseeing-rome-hop-on-hop-off-bus-tour) sounds convenient, I'm traveling on a budget and wondering if there are cheaper alternatives. Are there any affordable Rome bus tours or guided transport options that offer similar value? Maybe local buses or walking tours combined with a travel pass? I'd love to hear how budget travelers managed to explore Rome efficiently without spending too much.