Hi Darius, yes you can enter the Roman baths, it takes a while for ones eyes to adjust to the light but once inside they are pretty much intact (the baths that is ), in fact there is nothing on the whole trail that isn't accessible as nothing is cordoned off.
hi
if you know where porto azzurro hotel is, then it is simple to find the heritage trail. there is a hill next to the hotel, go up the hill and before you go right (where the road continues) you will see a few signs. on one od the signs there is written "archaeologicak site". the sign pionts to a narrow walkway (the walkway is stony). there u have the heritage trail.
the trail is a beautiful one. you can go many ways and all are wonderful