I haven't been yet, but my family will be in Puglia this July. This was the advice I received from an old acquaintance who now lives in Carovigno (near Ostuni):
Beaches - A combo of rocky terrain and patches of sand. As you get further north, my impression is that the shoreline tends to get rockier. A lot of the coastline is sort of scalloped, so for some of the beaches there are strings of sandy enclaves divided by rocky terrain (e.g., Torre Pozzella, north of Santa Sabina). if you come upon a beach and it's too crowded, scramble over the rocks and see if there is another mini-beach. Tho sometimes all you find is more rock, so take a look at Google maps before you go. And mind your feet - they're not rolling rocks, more the slicing kind.
The beaches by me (i.e.,in Santa Sabina) are tiny and crowded - there are a few a bit north (like Mezzaluna) that aren't bad, but if you're looking for a proper beach, go further south. There are loads, but these stand out:
Pantanagianni - sandier than most
Torre Guaceto - also a nature reserve.
I've also been trolling Instagram, and while I realize IG is not real life, it's led me to compile this list of Pugliese beaches that look inviting:
Ionian Beaches/Towns:
Porto Selvaggio
Gallipoli
Punta Pizzo
Punta della suina (Gallipoli)
Punta prosciutto
San Pietro in Bevagna
Sant’Isidoro
Piri Piri Lido (beach club)
Santa Maria di Leuca (tip of heel)
Adriatic Beaches/Towns:
Castro / Grotta Zinzulusa
Santa Cesarea Terme
Otranto (Bastioni & Alimini beaches)
Conca Specchiulla (Otranto)
Baia Morrone (Otranto)
Grotta Sfondata - Baia Mulino d’Acqua (Otranto)
Adriatic Beaches North of Otranto & SE of Lecce:
Tricase
Marina Serra
Torre dell’Orso
Torre Sant’Andrea
San Foca
Grotta della Poesia
Grotta Verde Marina di Andrano
Roca Vecchia
Jess, please come back here and update us after your trip!