I support your right as an American to gather and to have your voice heard, just make sure your doing things legal so the police have no reason to brutalize you.
but here are a few helpful tips in case you happen to be targeted anyway.
bring milk - it can be used to wash out mace from your eyes and shortens the duration of the burn.
if pepper spray is burning your skin use a solution of 1 part chlorine bleach to 5 parts water. DO NOT USE FOR EYES.
bring a hospital mask and vinegar(apple cider vinegar or lemon juice) - douse the mask with it and breathe through it. It helps cancel out riot gas, although you may have to re douse it occasionally.
swim goggles with a tight seal can help protect the eyes.
bring a solution of water and 5% sodium bisulfate to decontaminate yourself from tear gas.
wear clothing that cover as much of your body as possible and sinch the cuffs closed. if you find yourself in tear gas your first instinct will to be to panic. you will cough, throw up, have burning vision, and possibly a 3 foot trail of snot gushing out your nose.
Do Not Run, as you cannot see and will most likley run into something big and painful.
Breathing will be labored. the effects usually last 7 - 15 minutes. If you have a respiratory problem bring your meds/inhalers. do not touch your face or any other part of your body as the roit agent will spread. bring an extra change of clothes to change into. tear gas crystallizes so it will be in your clothes until washed.
Just some helpful tips from some one who has to go into a tear gas chamber every year. Be safe.