If you have no signs of it (asymptomatic), it will show up in a blood test after 6 weeks-- it takes time for the antibodies to build up. If you have it with signs, within a few days to two weeks. Any partner that is infected with the herpes virus has a moral responsibility to tell their partner prior to a sexual encounter. 50% of infected persons do not-- out of shame or they don't care. Victims can seek damages when this occurs. Check out: http: /stdlawsuit.com/do-i-have-a-case/.

Any infected partner that says using a condom or taking antiviral drugs completely protects you from herpes is either ignorant or in denial. According to an article in the New York Times, http://consults.blogs.nytimes.com/2010/06/18/giving-your-partner-herpes/, a condom alone is roughly 30% effective. Antiviral drugs alone are roughly 49% effective. The only way to avoid herpes is to avoid sexual contact with an infected partner.  Anybody with multiple sexual partners is at risk of being infected with herpes. Herpes comes with life- long issues and takes years to accept the consequences of living with herpes (I haven't yet). Personally, I believe both partners should discuss these issues together with a knowledgeable treating physician before having sex for best results. 

Remember, someone who is not upfront about this is not honest. Without honesty, there is no trust. Without trust, there is no relationship.