Although the above have stated that you don't always need to use a capo when playing in different keys -should you try a modal tuning such as GDAD or ADAD (and I recommend that you give
these tunings a try as the bouzouki as an accompaniment to
melody instruments or voice really displays its character to the fullest as a modal instrument) you will find that interesting possibilities will occur if your fingers let them and the capo can then be used as part of the instruments integral sound!
let go and the instrument will play itself and you can have fun!