I wouldn't (do something) unless (clause)

Use this phrase when you don't think you would usually do something, but you can think of some reasons that you would do it. For example:

I wouldn't be able to live in a big city unless I was rich enough to afford a huge apartment with a big outdoor patio.

So the meaning of the example at top is: "If a place is really hard to get around in as a foreigner, I might join a tour. In other situations, I wouldn't join one."

Notice that in the second half, the verb is past tense:

unless it was somewhere that's...

unless I was rich enough...

This is common in spoken English. For formal written English, you're supposed to use the subjunctive tense:

I personally wouldn't sign up for a tour unless it were in a country that's difficult to navigate as a foreigner.

sign up for (something)

When you "sign up for" an event or activity, it means that you fill out a form that shows that you want to join. For example:

I signed up for an aerobics class at the gym.

We decided to sign up this year for the Walk Against Cancer.

You can also "sign up" someone else (usually a child) for an activity:

Maybe we should sign Gavin up for violin classes. 

get around in (a place)

To "get around in" a place means to find the place that you want to go to, and to get there quickly and easily.

I've heard it's hard to get around in Los Angeles because of all the traffic.

I think Tokyo is one of the easiest cities to get around in because of how many trains there are in the city.

(do something) as a (something)

Use this phrase to talk about the situations and problems that one group or type of person has:

You can't really earn a lot of money as a teacher.