If you're looking for someone to tell you an exact time frame for when it's safe, no one can really do that. Cycling a tank, with no initial bacterial to seed things, will take 4-8 weeks. Seeding the tank with cured live rock, or live sand will speed things up, but there's no real way to know by how much. Biospira may... or may not speed things up. Others here have had great success with it, others have not.
Sooo... the only safe answer as to when it's safe to add fish (or a cleanup crew for that matter) is "when your ammonia AND nitrites have reached zero." And you're going to be the first one to know that!
And while low to medium levels of nitrates are not toxic to fish, you will want to do one or many PWCs before you add fish so that you can get your nitrates down to a reasonable level before you start adding fish. Doing them before adding fish is way easier because you can do larger % water changes (and thus fewer of them to reach the same goal) without being concerned about altering the water parameters too much, too fast since there's nothing in the tank.