I noticed in the quick guide that the BerryIMU connects to the SDA and SCL I2C pins on the Raspberry Pi. I currently have a Raspberry Pi 3 Model B with 2 port expanders already connected to those pins. Will I be able to connect the BerryIMU to the same pins or will it work if I cannot to any other GPIO pin?
You can connect them to the same SDA and SCL pins. You can have multiple devices connected to the same SDA and SCL pins. As long as they have difference i2c addresses, they will work.