I think the most important thing for a beginner (after consistency of course) is to build workouts around compound lifts and focus on getting a solid base in all the main lifts (squats, deadlifts, bench press, overhead press, pull-ups, rows). There's no reason a beginner can't make that happen and progress at a happy rate only training 3 days/week. There's also no reason it can't be done in 5 days; however, there's greater potential for burnout for inexperienced lifters training 5 days/week, especially when you try to do the same volume each workout.
Personally, I think 3 days/week is perfect for a new lifter until they learn how their body responds and recovers, and you have the discipline and self-knowledge to split things up effectively over 5 training days. If it's about getting into the gym a few extra days for the pick-me-up, you can always go to the gym and do some bike intervals, play basketball, racquetball, etc...Throw your routine aside and just have fun!
Oh, and you should definitely hit your legs more than once a week, ESPECIALLY as a newbie.