It is not advised to buy on July 31st, may be a day before that or two. You need to have all your stash on a wallet but segwit. The price will definitely rise and it'll be a new life for all the Bitcoiners here. Buy as early as possible and hold them well.
It is best to buy before July31 though we cannot predict the price of bitcoin. These past few days bitcoin has downtrend and today it seems recovering. I dont know if this is stable or what but the fluctuation is normal. So when dump buy if you have funds and hold.