as canasta said, its not pronounced as in english letter, its like in deutsche and in dutch (indonesia has been a Netherlands sovereign for about 350 years though!!!).
a --> /Λ/ as in 'cup' (cΛp)
i --> /ee/ as in 'eel'
u --> /u:/ as in 'tool' (tu:l)
e --> /e/ as in 'ten'
o --> /o/ as in 'lob' or 'toll'
some of the consonants:
c --> as /che/ in 'check'
y --> as /y/ in 'year'
g --> as /g/ in 'gulf'
