I served in Rwanda with no running water or electricity in my village. I wore glasses most of the time, but did have and did wear contacts on a routine basis. I would NOT suggest wearing them every day as that will obviously increase your risks.
In general, Peace Corps doesn't really want you wearing them because the conditions are not always ideal for things like sticking plastic foreign objects against your eyeball (are they ever, though???). You do want to be careful, though, because wearing contact lenses is still technically against medical policy and if you get an eye infection because of your contacts, Peace Corps is not liable for any resulting prolonged eye damage that may crop up later simply because you chose to break the rules.
That being said, I wore contacts in front of our docs all the time and they never gave me grief. But if you do decide to wear them and then get chronic eye infections or whatnot, they will make you stop wearing contacts.
Sidenote, if you do wear corrective lenses, bring 2 pairs of glasses. if you break one, Peace Corps will get you a new pair, but lets just say they their catalogs haven't been updated from 1960's styles. Hipsters will do alright, but the rest of us will be left wishing we'd brought a second pair.