You can always see the wireless network if it is set to broadcast the SSID.
Hiding the SSID is useless as any wifi analyser can still see the SSID when it is transmitted to a client.
What is important is the locks.
Here is list of wifi network in my home from a Mac.. hold down option key and it will list more details when you click the wireless fan.
In this list notice the padlocks.. all the wireless networks are protected by password. If you hover your pointer over any of those you will get further details.
This wifi is my neighbour..
I cannot connect to it unless I know his password..
Same with yours.. nobody can connect to your network without the password..
If you use a long password with mixed characters a quantum computer might be able to break it in your lifetime.. once they actually have quantum computers. This does assume your products are good quality and up to date firmware.. as various hacks are discovered now and then.. but security is very good on wireless and a person has to be in range to hack you anyway.. so count your neighbours and see if any look like a hacker.. !! A really good one.. with massive power cables running into their house.. perhaps an experimental fusion reactor in the backyard.
If any wireless does not have a shut padlock.. well then it is open.. ensure you are using WPA2 Personal security with a decent password.. then put the whole thing out of your mind.. you are safe.
N.B. Just one other point.. there is unfortunately a weakness.. not in Apple routers but many other brands that have WPS turned on by default.
Here is my main router.. an Asus.
This is its default setup.
You can see enough details above.. WPS is a system to make it easy for clients to join a password protected system.. it really helps with clients that have no interactive interface like other routers or printers etc.. unfortunately it is badly broken.. and should always be turned to OFF.
In Apple Airport turn on WPS via the utility.. but it is off by default.
