Yes, you can, and you don’t need multiple Ruuvi accounts.
It also doesn’t matter if two Ruuvi Gateway devices are within range of the same Ruuvi sensor, so you can improve signal coverage by increasing the number of Ruuvi Gateway routers in one or more locations.
Note that Ruuvi Gateway routers aren’t linked to your Ruuvi account, but instead route data from all nearby Ruuvi sensors to the Ruuvi Cloud, where only the assigned owners of the sensors can read the data.
This is why it is important that you claim ownership of all your Ruuvi sensors with the Ruuvi Station mobile app (requires to sign in first). Even if you don’t have a Ruuvi Gateway router.