It is possible to get really fast film up to ISO 1000 which will often allow you to take night time shots wthout the use of flash at all but it's worth remembering that the faster the film the poorer the picture quality. The reason why you need to adjust your settings if using fast film with flash is that if you're not careful the shutter speed will be faster than the flash - ie the camera will 'shoot' before the flash has actually come on. So before buying faster film do check that you've actually got the camera set properly for both the film speed and the use of flash.
Knowing a bit more about the type of camera you've got would help others offer more specific advice. For most holiday snapshots I now just use a compact Canon digital Ixus but I still have the trusty Olympus OM1 SLR which still gives fantastic results for eg portraits because it allows me to use slow film with a wide aperture so giving a slightly soft focus which generally gives a very flattering result.
SM