jeanne, take a look at the tips here Ricks money tips
What you'll see is that most people will use their debit cards to get cash from bankomats (ATMs) when they get there, to get the most favorable exchange rate (notify your bank about foreign travel first). There are other related issues about whether your bank or the ATM operator charge fees for these transactions, so if that concerns you, research it with your bank. Other travelers barely bother with currency, using credit cards (again, notify your bank) for most purchases. And then there are some that prefer to have some local currency with them before arrival so as to be able to cover immediate expenses (taxi, coffee, pay toilet, etc.) without searching for an ATM. You can get Swiss Francs from your bank, AAA, or an airport currency exchange, but note that you are really buying currency, not exchanging it, so any of these sources can set any rate they want and charge any fees they want. So it pays to have an idea of what its costing you for the convenience.
The casino will probably relieve you of the need to get rid of excess francs at the end of your stay.