I am sorry for this delayed reply to your gardening question as we are transitioning to a new Q&A system. I hope this reply is not too late to be of help.
Give the sod a few weeks to get roots down and then begin mowing. Weed and feed is not good for St. Augustine once temperatures rise to the mid 80's or above. For now just fertilize, water periodically and mow regularly to get your turf going. It will choke out most weeds if it is strong and healthy. If some remain you can treat them this fall or next spring.
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