When you arrive at the airport you could travel to Newark by train but if you dont know your way around it may be easier to use cabs. The trip is only around 24 miles long so should take 40 minutes depending on traffic. This may be the most hassle free option as it takes your straight from A to B, but the fare will vary depending on the time of the journey.
Another option would be to take a coach from La Gurdia to Newark Airport. Or the New York Airport Service Express Bus can take you to a connecting bus service in New Jersey. If you are looking for advice on Fares and Schedules you could call the following numbers.
New York Airport Service Express Bus: (718) 875-8200
PABT Bus Information: (212) 564-8484
At the weekend it is really easy to take a coach into the city. Since you are already located at the airport you wont have far to walk until you find the bus station. Here you will find a shuttle service where the coaches make the trip into
New York regularly throughout the day. This would also be the cheapest option and i think the easiest as the coaches as so close to your hotel.
Also if you would like to know about transportation in New York you will find the following link useful
http://www.destination360.com/north-...transportation