Laptop speakers are not going to give you a decent flat sound that will allow you to mix. Neither are desktop speakers combined with a bass amp. Sure, you can use them, burn sample discs, then listen in every possible listening environment/system to see how it sounds, but it'll be tough.
Yes. Even a cheapo set will be useful, as would some decent stereo speakers if you had access to some. I'm sure it could be done by some expert but I couldn't imagine mixing on my laptop speakers. They're awful. Their ability to sound good is even less than my ability to make music sound good !
I'm hoping you don't even mean to ask -- Your monitoring chain is by far, the absolute most important purchase you will ever make as far as audio is concerned. Every single sonic decision you will ever make is based on the accuracy, consistency and quality of the information between your monitors and your ears. Nothing else even comes close. You will only ever be as good as your monitors allow you to be.
And (I should've mentioned earlier) get the best ones you can possibly afford (and hold off to save more if you can't afford something decent) -- Not the cheapest ones you can get away with.
I never got rid of my first set of monitors. I still use them and a/b with my Morels. It is always nice to hear
things on different speakers. Like mjbphotos said, burn to disk and listen on many formats.