PEAP will secure the connection between your wireless client and the wireless access point relatively well. Whilst probably not your concern, the weakness in this system is the identification of users - usernames and passwords used for PEAP can easily be re-used on devices, whereas EAP-TLS would provide stronger authentication through the use of certificates.
What you are probably interested in is the security of your data from your wireless client through to the internet. The strength of your wireless security (between your wireless client (WiFi Cli) and the wireless access point (WiFi Ap)) tells us nothing about the security of your company's internal network.
|-------- Office Network --------|
WiFi Cli <---------------> WiFi AP <----------------> Internet
If you are connecting to a HTTP website, the reality is your company can see all of the content in clear-text relatively easily.
If you are connecting to a HTTPS website, your company probably can't see all of the content (without a HTTPS inspection on a capable proxy) - but they can see what the name of the site is. This means they could see you are using Snapchat or Facebook generally, but not the contents of the pages, messages or images you send/receive.
Whether you should be using it for that purpose, however, is another question entirely!