So that the other Wi-Fi device knows an android phone (with wi-fi enabled) is nearby?
And if you are using a open wifi network for example on a café, then you can be watched with a simple app called droidsheep.. But all devices can be detected by such app, even mac and windows and IOS... So just be careful when you are using a open wifi network...
When you say that Wi-Fi is enabled I'm taking you literally: that Wi-Fi is enabled but is not actually connected to an access point (hotspot).
So the answer is no.
Just enabling the Wi-Fi on your phone does not make it visible to other devices. It just sits there listening passively. No one around you can see your wi-fi or get it to respond.
If you set your device to be a Wi-Fi hotspot (typically for tethering purposes) it will emit a signal called a beacon that allows other devices to see it.
Also, if you turn on Wi-Fi Direct then it can be seen, but this is a new feature in Android 4 that is not widely used yet and I don't know much about it.