Depends on your needs. If 200ms is really too slow, then you'll probably either need to get a VPS in the East Coast data centre if you want to stick with DreamHost, which might bring your ping time down 50ms or so, or move to a different host.
Moving to the East Coast data centre will make your ping time faster, but any customers you have in Australia, for example, will have longer ping times. Colocation at several data centres around the world is the only way to bring the load times down for everyone.
A CDN would help if your site is relatively static.