MAYOR Bloomberg — who has noted how many restaurants are suffering because of the recession — got a firsthand taste of how bad it can get when he joined the going-away party for longtime aide Jonathan Werbell the other night at Trigo in SoHo. “The restaurant just opened and it’s already going out of business,” noted Deputy Mayor Ed Skyler during a speech at the Citizens Budget Commission. Famed chef Terrance Brennan is going to take over the cavernous space at 268 West Broadway this month and turn it into Bar Artisanal, an offshoot of his popular cheese- focused eatery.