If a person sees Cydia on the device, they will find out that you have a jailbreak installed. There is no way to hide that fact. If you want to jailbreak on iOS 7, use Evasi0n.
If something doesn't exist because you don't know it, the world ceases to exist.
Both Springtomize and SBSettings can hide Cydia from the user. Hidden apps don't show up in the search.
Short of the user plugging the phone into a comp to look for Cydia or to try to jailbreak, it's not detectable at that point.
The bigger concern wouldn't be seeing Cydia. It would be what happens if there is a rare mobile substrate reboot into safe mode. That'd look pretty strange on a "stock" device. Additionally, several apps on the AppStore pop up a message to tell jailbroken phones they won't work. Skype is one of these and a rather popular app.
If you're worried about seeing Cydia, you don't understand the problem.