300DPI is high end glossy art mag resolution. (no idea about this next bit just an educated guess) I think you will find most home printers top out at 300dpi anyway.
Most are capable of far higher than 300dpi - my three year old very basic HP Deskjet will go all the way up to 1200dpi, and it's nothing special as far as inkjets go!
I do signage at 600dpi usually, although as Surv said, 300 is usually acceptable. Using good paper helps; cheap office-grade stuff doesn't hold ink as well as slightly heavier papers or light card.
No access to a colour laser currently, although I'd really like one for a sheetful of colour signs and posters I've been accumulating! Inkjet printouts run or smudge when damp or wet, which makes weathering and glue more difficult. You can get nice results with dry pastel dust weathering, though.