Dreamers

1. Dreamer - someone who is dreaming
Sleeper, slumberer - a rester who is sleeping

2. Dreamer - someone guided more by ideals than by practical considerations

Idealist
Don Quixote - any impractical idealist (after Cervantes' hero)
Romantic - a soulful or amorous idealist
Visionary - a person given to fanciful speculations and enthusiasms with little regard for what is actually possible

3. Dreamer - a person who escapes into a world of fantasy
Escapist, wishful thinker
Daydreamer, woolgatherer - someone who indulges in idle or absent-minded daydreaming