Signal can be a bit weaker on the watch up here in Canada but is otherwise adequate. The problem with Apple Watch cellular when not using an iPhone to forward data is (1) battery life on LTE is terrible compared to data over Bluetooth, using wifi, or turning on airplane mode and (2) call forwarding from iPhone to Watch, on some Canadian carriers, is charged per minute due to a carrier bug (Telus) which you can call to get refunded but is still frustrating. Normally calls go to your iPhone and the voice is forwarded to the watch over Bluetooth, I believe. Basically the Apple Watch more often acts like an AirPod than a cell phone.

I end up carrying my iPhome with my Android phone to avoid this. I mount the iPhone to my bike/scooter when available using Quad Lock waterproof cases.