Based on my experience, it appears that you can - although that is not recommended since you will consume a lot of data. My L1020 seems to have partially downloaded the update before, but when I noticed that I switched to Wi-Fi for the remainder of the update. Others may confirm or debunk this for me.
By the way, users are encouraged to post their queries in the respective forums. The Ask a Question forum is reserved for time-pressing matters and for guests who don't have an account yet.