Hi @janetb in Jerusalem -
Bad news first. Regretfully, I don't think there's a way for a user to toggle off the suggested topics toolbar.
Some good news. As you login and use the system more and more, it will learn (sort of) what to put there that might be of use to you. Even if you are logging in, another reason it's not making particularly good "suggestions" right now is because we have so many users replying by email and not logging in. So it isn't collecting good data it can use to make good suggestions. Some more good news, Discourse is a community-created software package - what they call "open source." So everyone who uses it contributes to the code base. There are many folks toying with that particular feature, so I'm hoping it will get better.
I too am not particularly impressed with suggested topics. I'm going to see if the next few upgrades make it better, if not I may end up writing something to go there that will be more useful.
If you are really interested in the technical discussion of how that works (I won't be offended if you aren't!), there is a thread about it here.