declare @schema table (tblName varchar(128), colName varchar(64), colLen int)
insert into @schema
  select SO.Name, SC.name, convert(int, sc.length) as Length from sysobjects SO
  join syscolumns SC on SC.id = so.id
  where type_name(SC.xusertype) in ('text', 'nvarchar')
  /*
   and SC.Name NOT in
   (select name from syscolumns where name like 'DF_%')
  */
    and SO.xtype <> 'P' and SO.name like 'tbl%'
  order by SO.name, SC.name
select * from @schema

declare @tName varchar(128), @cName varchar(128), @len int

declare @altString nvarchar(512)
declare Change Cursor for select * from @schema
open Change
fetch next from change into @tName, @cName, @len
while @@FETCH_STATUS = 0
begin
  -- 
  set @altString =  'alter table ' +  @tName + ' Alter Column ' + @cName + ' varchar(' + cast(@len / 2 as Varchar(4)) + ')'
  EXECUTE sp_executeSQL @altString
  fetch next from change into @tName, @cName, @len
END
close change
deallocate change