They will often post with the closing of your first credit card statement after you have met the spend requirements.
Even if the OP applies for the card, gets the card, meets the spend requirements, and then gets the miles posted in 3-8 weeks from now, she might have difficulty then finding award availability to Paris over the summer, right?
I think she's probably better off just buying the tickets to Paris now. If she waits two months and then is unsuccessful booking with miles, she may find that the cost of buying tickets has gone up by then.