Yes, iMessage texts are encrypted from end to end. It is not as secure as the Signal texting App, but iMessage is the next best thing. After reading this article, I discovered that if you use iCloud to back up your iPhone, the texts in iMessage are NOT encrypted. The article describes why Apple does not encrypt your iCloud stuff, it has something to do with the FBI. I have turned off iCloud backup on my iDevices, just backing up to my Mac.