My Apple Watch is not letting me send messages to an android user

Turn on SMS on your iPhone.

Settings->Messages->Send as SMS. Also check your cellular plan to see if you have texting privileges and if you are paying for it.

Read the footnotes on the following page

https://support.apple.com/en-us/HT205547

"1. To receive SMS, MMS, or push notifications from third-party apps on your cellular Apple Watch, your paired iPhone must be powered on and connected to Wi-Fi or cellular, but it doesn't need to be nearby. You also need to be signed in to iMessage on your iPhone."

And I can verify that this works, as I've exchanged SMS TEXT messages with Android users.