Don:

For US properties, it is a property-by-property decision to open the lounge or make it accessible during the weekend. That's why there is the following thread in this forum: http://www.flyertalk.com/forum/marri...-weekends.html

Here's the entry for the San Ramon Marriott (where I have stayed and had the same experience):

San Ramon / Marriott / CLOSED Weekends & Holidays; buffet breakfast in restaurant; 2 i-net terminals + free wifi; report of comped free parking (not sure if it's a bennie or one-off); 09/21/14 update