The phrase "You don't want to go there" has seldom seemed more appropriate than when applied to Angels of Mercy Hospital, setting for the new Steven Bochco drama "City of Angels." Here is a place so dismal and dreary that even the cockroaches must have moved on to higher ground. It's a medical show to remind people who hate medical shows why they do.

CBS is giving the series a premium time slot for its premiere tomorrow night at 8 (on Channel 9), before moving it to Wednesdays at 8, where it's likely to languish at best, expire at worst. This is one of those series that were virtually born languishing. It's languishment for the entire family--if the entire family is in a really rank, foul, grouchy mood.

The one good thing about the otherwise substandard medical drama is that it gives employment to a large number of African American actors, and good ones, too. The absence of black faces in episodic TV shows has been conspicuous lately, and the networks have come under heavy criticism from advocacy groups. You can't correct a flagrant imbalance with just one show, however--though that may be what those behind "Angels" imagine they are trying to do.

Of course, there's lots of bad news to go with the modicum of good news. Angels of Mercy Hospital may be largely staffed by ethnic minorities, but it is depicted as being even more trouble-prone, accident-prone and incompetence-prone than other TV hospitals. It doesn't even have accreditation, a problem that the new medical director, played by the very vivid Vivica A. Fox, is supposed to rectify.

Her arrival is one of the plot lines on the premiere, which finds many of those who work at the hospital either fumbling about or getting into petty arguments with one another. The hospital is organized along show business lines; there are executives over executives over executives, just as TV shows have producers upon producers upon producers.

Perhaps this bad television show is also a metaphor for a bad television show. Or something.

As for the physicians, they tend to behave like spoiled, bratty actors rather than medical professionals. You wouldn't want them touching your appendix with a 10-foot pole. Come to think of it, that would probably be their first line of treatment.

The actors playing these actor/doctors are, actually, first-class, starting with Fox, who is extremely beautiful in the extreme, but brings guts as well as glory to the role. Blair Underwood, conversely one of the handsomest actors in existence, plays the acting chief of surgery. And guess what, these two pretty pretties have a back story. Yes, it seems that seven years ago, he chickened out on marrying her just three days before the ceremony.

Gosh. It seems so--so--so corny.

Also in the cast are Michael Warren, minus the head of artificial hair he wore on "Hill Street Blues," as another hospital official, the chief executive officer (no wonder nobody can get a doctor in this place; everybody's an executive); young Hill Harper as young Wesley Williams, an ambitious resident; and, seen briefly tonight, founding "Saturday Night Live" cast member Garrett Morris, playing a doctor who takes a naughty peek at the naked corpse of a dead rhythm and blues singer.

Apparently the singer was so fat she fell to her death through a termite-weakened stage. Yes, Bochco gets the show off on one of his trademark "shocking" notes, only this one is so self-consciously shocking it isn't shocking at all. It's sad.

Among other regulars, Robert Morse--former musical comedy superstar--is a wry surprise as chairman of the Board of Supervisors (another executive--good grief!) except that in one twinkly, fey and repulsive moment, he reveals himself to be a foot fetishist--not that there's anything wrong with that, but the way it's handled, it just makes you groan with agony.

Phil Buckman, a talented and likable kid who has paid his dues on many TV shows and movies, co-stars as a young Jewish resident. Among many other credits, Buckman stole all his scenes in the foolish horror film "An American Werewolf in Paris" last year. Buckman's character unfortunately gets humiliated more often than is necessary and is made to seem spineless. He lets a loudmouth patient refer to him, to his face, as "Palisades Jew-boy" and offers nothing in the way of reprimand or even a retort.

Soppiest of the subplots has a dear old granny wanting to put off emergency surgery because it will mean her dear little grandchildren will be left home unattended. It seems her daughter and their mother is a crack addict spending time in the slammer. That saintly new medical director goes about trying to arrange a humane parole.

Fox definitely has the authority to run a hospital as well as run a TV series, but she and the rest of this outstanding cast deserve better ones. "City of Angels" offers a world that is bleak and struggling and desperate, but somehow glibly so, superficially so, devoid of emotional clout. The welcome multiethnic casting means it isn't "just another" doctor show, but that's the only thing keeping it from such a fate.

It's got an edge, yes--nothing more important these days than having an edge, is there? But it uses its edge to slash its own wrists.

CAPTION: Blair Underwood and Vivica A. Fox can't save the medical drama "City of Angels.

CAPTION: Guest star Fran Bennett, left, and series star Vivica A. Fox in Steven Bochco's languishing "City of Angels," premiering tomorrow night at 8.