My advice would be similar to Contadino's (ie avoid Italy's Adriatic coast north of Puglia).
The SS16, the main road along the coast, would be my hot favourite for Italy's Most Boring Road. It's the sort of road where even the sight of a petrol station (and therefore a bar and a cup of coffee) can raise your spirits like seeing an oasis in the desert. If you zoom in on the map you'll see that for much of the way it runs beside the rail line. The rail line is on an embankment and so you don't even get to see the sea. Check Google Streetview and you'll see what I mean.
There is an alternative to the SS16: the
Ciclovia Adriatica a lot of local authorities in seaside resorts have invested in cycleways.
And if you're thinking unspoilt beaches, forget it. Sadly a lot of this coastline has been taken over by private lidos, and in the tourist season people pay serious amounts of money to rent a few metres of space on the beach (OK technically they are renting an
ombrellone and a couple of sun loungers, but the effect is the same).
My suggestions would be to either head further north on the Croatian/Slovenijan coast and then get a ferry to Venezia (IIRC there are ferries from Rovinj and Pula). Or even continue to Trieste or Grado and then up into Slovenija and Austria. I suspect though that the Croatian coast may be just as over-developed as the Italian coast.
Alternatively if you really want to do the Ancona thing, one possibility to consider going over the Apennines into Umbria. The regions have spent a lot of money building a faster link over the Apennines via Fabiano (the SS76). The old road is still there and should be blissfully quiet (I did sections of it a few years ago). I would research this alternative carefully though.
You don't say when you are planning to travel, but seriously, if you possibly can, avoid going in August.