I wouldn't delete your account (in case Reddit tries to replace the deleted comments as they have been doing). But I would unsubscribe from every subreddit.
Additionally, if you have any very useful comments/posts, repost them to Lemmy and then edit them to leave some information that will redirect users to your posts in Lemmy. That way good information isn't lost and you'll help to slowly drive users towards Lemmy over time.
Either way it's probably worth it to hold onto your account for a while longer to verify that there weren't any issues with your posts/comments being deleted.
I've been replacing my posts with gibberish (google "gibberish generator") and a link to lemmy.
Be aware that /r/AskReddit has some automation that will delete your post if they detect some script. I don't know how it works, but so far the trigger for me seems to be any link to the /r/apolloapp post where Christian posts his call logs.