First of all, I have to say spotting at BBU is not (yet) officially allowed.
You can stand on the other side of the main road (DN1) and you will have no problems with security. The aircraft come in quite low to land on runway 07.
However if you have more time to spare, and have access to a car you can try "the mound". Keep a low profile and you shouldn't have problems with security. Here is a screenshot from GEarth showing you how to get there. Light is perfect here until late afternoon and aircraft can be seen from very close range, taxiing on Delta.
If you give us the time when you will be available, maybe somebody from our forum will be able to come with you.