How to test if wifi is secure?

Hello everyone, I recently moved to an apartment/condo that provides free wifi internet. Today, we had a building meeting and I mentioned that the wireless comes up as insecure. This is scarey because some people rent their condos on a daily or weekly basis. The connection is also shared by Starbucks. He said the wireless is secure...I called the isp company...They said it was secure... I can not believe that this wireless is secure...and... to my knowledge if this is the case...it would be the only time a connection that is shared with Starbucks is secure. Is there a way for me to test the connection to see if it is secure ... so that no information can be hacked? Is there a better way to technically ask the isp if it is secured and how can they prove it to me? Thanks to all.

Dupe thread, closing