If I get a cab at 445p,should we be able to make a 700p flight? Assuming we get to LGA about 530p,would'nt that be enough time ?(90 mins)

Barring extremely unusual circumstances, your assumptions are correct. Even if it ended up taking you an hour to reach LGA (highly unlikley at that time of day on a Saturday - most of the traffic on weekends is heading into the city at that time of day), you'd have 75 minutes at LGA before the flight. I flew out of there last saturday at mid-day and the airport was practically empty. Check-in, security gate etc. took me about ten minutes in total - you should be fine.

If you are taking an international flight, you are kind of cutting it close. Most airlines want passengers there two hours in advance. With domestic flights, about 90 minutes in advance.

Leaving Madison Square Garden, there's lots of traffic and lots of pre-theater traffic.

You'll probably be okay leaving at 4:45 but IMO it's a little tight. Also, as you may already know, the airplane closes its gates to the minute, even if they have to sit on the tarmac, in order to get those on-time ratings.

Correct me if I am wrong but I thought all international flights flew out of Newark and JFK. LaGuardia is only a domestic airport?

Well I've flown out of LaGuardia to go to Canada and went through international customs, etc. so I consider that 'international'

What airline / terminal are you taking? I usually fly Delta and thank God for their own terminal at the end. You do not get dtuck in that long line of cars, cabs and buses.

Always assume that there will be at least one accident on the FDR Drive and at lease 2 work crews and closed lanes. You can be at the airport in 1/ hr and also 1-1/2 hr. You never know.

A lot also depends on the weather.

Thanks for you guys/gals advice.I'll be flying back to ATL on Delta.Thinking now about spending a 2nd night(mom wants to have more time to shop,ect!