Did you already read the City by City thread at the very top of this Hawaii forum?

There's more than one review of Kailua.
I think Kailua is "safe". It's not known for criminal activity. I don't know what your budget is but Kailua doesn't have a lot of condos or apartments for rent. There are some. It's a town with mostly single family homes.
You do have more options to go where you want compared to some other town on the island. You can get out of Kailua either by going over/through the mountains - Pali Highway, the Likelike Highway (if you go into Kaneohe) or the H3 Interstate (hahaha!) Highway. Likelike is pronunced "leaky leaky". You can also take Kalanianaole Highway from Kailua to town although it is a slower longer way to get out, IMO. There's a decent public bus transportation system. I have family members who bus it to town. Depending on where you're going to in town, you may have to transfer to another bus at Ala Moana Center or in Downtown.