Are gonorrhea and chlamydia usually symptomatic for males?

Usually yes: Gonorrhea and chlamydia infect the urethra, the tube where the urine and semen come out. An infected man gets discharge from the urethra and also a burning sensation when he urinates. However, some men might have mild symptoms and manage to ignore the discomfort. Having several sex partners and not getting checked (and cured if needed) in between partners, makes it easy to transmit these diseases.

Not necessarily: Unless the infection produces prostatitis and pain, STD's can go unnoticed without testing.