You should still be yourself, but dress for comfort in Oaxaca. Summer in Oaxaca will be a bit cooler than New Jersey, but there's no air conditioning, so keep that in mind. It'll probably rain a bit every day, and it cools off when the sun sets because the city sits about 5,000 feet above sea level. However, the sun's rays are very strong during the day, so be prepared to protect your skin.
Bring clothes for 7 to 8 days; you can take them to the laundry, where they will be washed, dried, and folded for you.
Don't plan on shopping for regular clothes or shoes in Oaxaca, as they are expensive.
Airport Stuff
Please check your individual tickets for baggage rules and costs.
Generic Stuff to Pack
Earplugs (Oaxaca is many things, but it is not quiet.)
Sunglasses
A Hat
Sunscreen
Mosquito Repellant (you can also buy in Oaxaca)
Walking Shoes/Sandals
Flip Flops (for apartment and shower)
Light Raincoat
Small Umbrella
Smallish backpack
Small across-the-body purse or bag
Refillable water bottle
Bathing Suit (optional)
Medicine (you can find most over-the-counter stuff there, but make sure to bring your prescription stuff; also, if you can get your doctor to write you a "just in case" prescription for food poisoning, I would recommend bringing it with you)
Pepto tablets
Shampoo/Conditioner (if you're not picky, you can buy it there; if you have a specific brand that you need, bring it with you)
Laptop (strongly encouraged, but a tablet will do, too)
E-reader (optional)
Headphones (optional)
What to Wear:
Bottoms: (in a breathable material)
Capris
Jeans
Shorts (many Oaxacans don't wear shorts, but you can if you want to!)
yoga pants (if you want to work out)
Tops: (probably want to wear cotton)
Tank tops
T-shirts
light, informal sweater
light scarf
light jacket
Going out at night:
You can pretty much wear whatever. You will see men in ties sometimes and women in heels, but also hippies!
Other Stuff:
Extra underwear!
Sleep stuff
exercise clothing (if you plan on running or going to the gym)
What NOT to Bring:
A suitcase that you can't pick up by yourself!
A heavy jacket
formal clothes
expensive jewelry
food
clothes that need ironing
shoes that you can't walk in
What to Buy When You Get There:
A travel journal
A notebook for the language classes