Sperm with either haploid compliment do not " prefer " an acidic environment, but have mechanisms to deal with one and buffer the acid so that they can enter the ovum.
If sperm with the X chromosome prefer a acidic enviroment then how do you give them that?
There is more involved in helping have a girl than just an acidic environment. You need to know when you ovulate and have sex 2 1/2 - 3 days BEFORE that. The males are faster swimmers but die of quicker. You are also naturally more acidic before ovulation than you are during. Also if you orgasm you secrete a substance that makes the environment more alkaline so you do not want to orgasm while trying for a girl. You should also be able to order pH testing strips online or at a health food store. Once you know where you sit on the scale. You can up your acidity level slightly by simply eating acidic foods for a few days. An acidic diet for conceiving a girl should include plenty of calcium in the form of dairy products as well as strawberries and raspberries, all in unlimited quantities. Cheeses, pasta, fish, green beans and cucumbers make up the next tier and you can eat them almost without limit, while you should consume some foods including cranberries, lamb, chicken, rice and corn cereal only once a day. This diet allows no alcohol. Also the diet should be for the daddy to be too, not just the mommy.