To hide the filter, just set the filter type to 'label', or set the 'defaultFilterType' property to 'label' and enable what fields you want to filter.
var dg = $('#dg').datagrid({
defaultFilterType:'label'
});
dg.datagrid('enableFilter', [{
field:'listprice',
type:'numberbox',
options:{precision:1},
op:['equal','notequal','less','greater']
},{
field:'unitcost',
type:'numberbox',
options:{precision:1},
op:['equal','notequal','less','greater']
},{
field:'attr1',
type:'label'
},{
field:'status',
type:'label'
}]);