HENS VS STRAIGHT
Why not you ask? Well because presumably you are interested in having chickens for the purpose of egg laying. In that case you want hens. If someone tells you, "oh you'll get mostly hens when you buy straight run", they are ignorant or lying. You could end up with anything, including all roosters!
Roosters can be both loud, aggressive and useless if you have no specific purpose for them. There is nothing more obnoxious than having the ear piercing screaming of a rooster before you are ready to wake up at say 4 am, except a neighbor who subjects you to the same without your approval, which puts you out of control of your own quality of life. Plus of course they can eat their weight in feed every week. Chicken feed in not so cheap that you want to feed a bird that does nothing for you.
Now if your intention is to breed, then just be considerate. If you have neighbors close by and you suddenly bring rooster(s) into an otherwise serene atmosphere. Then you are being extremely rude and robbing them of their peace and quiet. Just because you have made up your mind that it's not a big deal doesn't cut it. That is not a fair justification. You simply should not do it without neighbors approval. Just imagine if they suddenly built kennel and deposited about 10 or 15 barking howling hunting dogs, which is legal in many counties.
WHERE TO BUY
Like to support local farms as much as possible but unfortunately
you are most likely going to get straight run. The alternative is
buy from a large hatchery that employs experts who sex the chicks
or buy adult hens locally. Many small farms raise pullets for sale.