I'd like to use a Bluetooth symbol which will be a visible part of my product for sale.
Can I legally use this graphic?
Yes. It is a "registered symbol". However....
The Bluetooth symbol is specifically designed to be included on product packaging and marketing materials in order to indicate to the consumer that the item is "Bluetooth aware" or capable.
With this in mind, of course you can use the symbol on packaging for your product. Merely ensure you stick to the usage guidelines.
Here is a PDF LINK to the Bluetooth "Brand Book" which details usage and permissible display.
Note that you are not permitted to use the Bluetooth symbol in something like a "logo". Rather, merely as an indicator your product/service is compatible with Bluetooth devices.