Summer plants: plant out after last frost in April or May.  
 
Cucumber plants are sold in 2.5-3" peat pots or plastic pots.  Peat pots can be planted directly in the ground, but I recommend tearing strips in the sides and bottom to allow roots to quickly grow into soil.
 
Space plants about 12-18" apart.  Train onto a trellis or allow to grow across the ground.  Vines of most varieties will spread up to 8' around the base of the plant if left on the ground.
 
Variety information:
Manny: Extremely productive and disease resistant plants that put on smooth-skinned, burpless fruits.  Our favorite year after year.
Gateway: American-style slicer with excellent disease resistance.  This becomes our favorite late in the summer when bugs are rampant and disease spreads like crazy.