Not trying to rain on your parade....but unless you're having single colurs, cut vinyl isn't a great option...if you start layering up colours you end up with a lot of edges to lift and catch and a shabby looking sticker in no time...if you need single colours with reasonably big letters though cut vinyl makes sense as it's far cheaper than printing.
Very good point, if you want decals for a full on restoration then your better off going for the real deal or getting them printed on clear and cut on an i-cutter. If the stickers are to cover a polo bike or something like that then vinyl is ideal. Or like scott said, big lettering with clean edges is also fine but small fidly stuff can/will pick up dirt and scuff over time. But multiple colours are not a problem at all it can be as many colours as you in theory so long as they don't all overlap.
Very good point, if you want decals for a full on restoration then your better off going for the real deal or getting them printed on clear and cut on an i-cutter. If the stickers are to cover a polo bike or something like that then vinyl is ideal. Or like scott said, big lettering with clean edges is also fine but small fidly stuff can/will pick up dirt and scuff over time. But multiple colours are not a problem at all it can be as many colours as you in theory so long as they don't all overlap.