I do not what countries you'll visiting but I second the recommendation for iPass. I've used them as emergency for the past 5+ yrs. They offer dial-up, DSL and wireless connections in many countries (as well as USA).

Whenever I can't get high speed connection, iPass always has a dial-up modem telephone for a solid connection. I pay a $2.50 monthly fee plus actual usage fee - in the instances when I've had to use them their fees were very reasonable - even overseas.

Btw, their dialer for mac not as comprehensive as for pc users....