Assuming you mean small-scale wind turbines, I would say no. One turbine will only rarely be directly upwind of the other one, especially if you orient the towers to reduce the chances of this happening. Another thing to point out is that the "blanketing" of one turbine in the wake of another is proportional to its size. Instead of trying to maintain a fixed "300 foot" distance, you are better off considering relative distance, scaled according to the size of the two turbines. 300 fee is very far if the turbines are only 4 feet in diameter, but very close if the turbines are 100 feet in diameter, of course!
Wind farms have more criteria to consider, too, when siting their turbines, but I don't think that's what you're asking about.
