Hotel Lero is apparently full, although some people have had success reserving a room through Orbitz. Here are some other options:

Hotel R is next door to Lero:

http://www.hotel-r.hr/

There are also many other hotels. Here are some web sites:

 http://www.dubrovnik-area.com/Eng/hoteli.asp
http://www.dubrovnikhotels.travel/Default.aspx
http://www.gulliver.hr/
http://www.gulliver.hr/iuc.php

Hotels Vis, Splendid i Komodor are in the same price range as Lero.