You should be bringing your own condoms with you, anyhow.
First, never expect a woman to have her own supply of condoms. There are far too many women who's idea of birth control is having her lover wear a condom that she expects him to supply.
Second, you should have already have an idea of what condoms you prefer to use, based on their sensitivity, durability, texture etc. A woman likely doesn't use the same criteria for choosing a condom as you do (Do think she knows whether Durex or Trojans feel better?) You could get stuck wearing some bathroom-purchased Tire-tread on your penis instead of your prefered brand.
As far as the scenario your discussing, I think it is quite rare, though not unheard of, for women to sabotage their birth control in order to get pregnant. The vast majority of women are sane enough to realize the magnitude of the decision to have a child. I think most women end up with unplanned pregnancies for two reasons 1) Sheer irresponsibility with using a safe, effective method of birth control or 2) The small failure rate cacthes up to them. Only a rare breed are stupid nd selfish enough to try and have a child they are unprepared to raise in order to get a child support check or to "trap" a man into marrying them. Anyhow, if you use your condoms everytime, you'll more than likely be fine.
And a big "Hell Yes!" to the male birth control pill. If what I'm hearing is correct, it's over 99.5% effective, has few side effects, is easier to take than the female pill abd us being preped for market use in near future. Sign me up!