The AGSMapView::addMapLayer returns a UIView. You can use it's hidden property to control the visibility of the layer. It'll prevents querying the server and drawing.
NSURL* url = [NSURL URLWithString: @" http://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"];
AGSTiledMapServiceLayer* layer = [AGSTiledMapServiceLayer tiledMapServiceLayerWithURL: url];
UIView<AGSLayerView>* lyrView = [mapView addMapLayer:layer withName:@"Streets"];
lyrView.hidden = YES;
Hope this helps!
Regards,
Nimesh