What is most important to you? Pick up to three things, for example: number of guests, good food, open bar, day of week, time of day, flowers, centerpieces, music, attire, attendants, venue, photographer, location, rings... Spend your budget accordingly on those three things and go cheaply on everything else. Stick to your budget - if you spend more on one area, then cut something out in another (e.g. no champagne toast, skip the cake and do pies/cupcakes/donuts instead, etc.)
Your biggest expenses will be the venue and number of guests. Based on your post, the number of guests is one of your top three priorities so particularly look to save on the venue. It sounds from your prices that you are looking just at big hotels. Try looking much harder - check out parks, halls, smaller inns, even golf clubs will be cheaper than a big hotel wedding. If you overspend in both of these areas, it's exceedingly hard to make it up elsewhere, because it has such a big impact on your budget.
And then consider: iPod music (or at least DJ), non-Saturday wedding, pre-owned dress & suit you can rewear and not a tux rental, not yet fully established photographer, skip flower centerpieces, few attendants (just MOH/BM?), wedding located not right in SF, a limited bar, make your own simple invitations, serve chicken instead of steak (or go ethnic), etc. Skip things that don't matter to you (favors? fancy things to cut the cake or cake toppers?), negotiate everything, and DIY as much as possible (buy on sale or with coupons). Accept gifts of friends to help you.
Note: Don't rely on people giving money at the wedding to pay for the wedding. Not everyone will give a gift, the gifts may be less than what you expect (and less than the cost of the plates), and often it's in the form of registry item so unless you plan to sell the pots or china, not terrifically helpful to pay for the wedding.