Parts of the delta can be sailed easily. The Sacramento river is about 15 feet below the top of the levies so
wind in some places is an issue, east of rio-vista for the most part as its a winding river below the levies. Lots of boat ramps to launch from, Rio vista has a city
ramp just to the right of the end of main street, as does the Delta Marina there. Easy sailing in that part of the river. Other marina's all over the place to launch a boat from. You could sail from Rio vista to the golden gate, but its LOT's O tacking heading west dead up
wind.
Same for the San Joaquin.
Here is a link to the marina's in the delta.
marina info
Big issues is summer winds (west winds) are generally 20-25, gusting 30+ knots every day from May to around September generally after noon, but some days 24/7. Sometimes the rivers get just a little rough for the smaller craft. Specially with an outgoing tide. October and November can be lovely as the winds moderate and the summer crowd calls it a year.