Ruth Benjamin has become a big fan of the Goo Goo Dolls.Not that Benjamin knows the difference between "Superstar Car Wash" and "Gutterflower" recordings. What Benjamin, general manager of the Hyatt Regency Buffalo, knows is that her hotel is booked solid this weekend, thanks in large part to Buffalo Place Inc.'s "Uncle Sam's Jam."Uncle Sam's Jam is a two-day free music festival, set for July 3 and 4 in Niagara Square, that will culminate with Buffalo's Goo Goo Dolls performing live for a concert that's being taped for a DVD set to be released later this fall."Our phones are still ringing off