This isn’t a recommendation on how you should vote … I don’t consider it any of my business to advise others on how they should vote :)
I found a note on my doorstep today advising me to: sign, put my address and date the back of the envelope. Perhaps this was meant to err on the side of caution … but you only need to sign the back of the envelope. The address is already filled in and there is no requirement to write in the date — if you are filing out your own ballot.
For the June 8th statewide election, you can even look up the status of your mail ballot. There is no tracking mechanism (yet) for the Measure E special election.