I have been told that when you grow outside the plants wont start flowering until late June -August. So my plants are already showing preflowers. So does that mean that I may be able to harvest early too???
There's many factors...mainly sexual maturity, which is based on the age of the plant, not photoperiod or anything else. Once sexually mature, they'll show you their privates. I grew my plants inside for about a month, a week or two outside and they showed me, around late May.
No, you wont. Preflowers and flowers are 2 very different things when it comes to this, your plant isnt ahead of schedule or anything, its just mature enough to start flowering while still in veg like it should be doing now.