Deployment of ISA in Small Cyber Cafe

Hi!
I just want to ask all u one question.
First of all I’m going so state all my data.

One cyber cafe : 20 Pcs
One ADSL (256 KBps) : IP :10.254.8.101
subnet: 255.255.252.0
gateway:10.254.8.1
P,DNS :203.81.71.146
s,DNS :203.81.71.147
One Pc for Cafe station
One Server for ISA.
IP scope for LAN : 192.168.1.1 – 192.168.1.22

how should i do (configure)?
in some tutorial, they recommand 2 Windows 2003 server including DC with DNS and ISA.
But is it possible to use one and only one ISA server?