I am 31 weeks almost 32.. and she just dropped last night. Only way I can tell is my pants could fit yesterday and I could button them nicely.. and today they won't even come close together.. so I know she had to of dropped have a lot of pressure down there too.
Nopeeee , the baby dropping is not a for sure sign of labor. My son has been always been dropped and upside down since 28 weeks and he's just hanging in there wanting to make me as uncomfortable as possible lol.