Q:

Options for setting up a DMZ and internal network with an ASA 5505 and a single switch

This is an attempt to clarify my original post which was too long.
My task is to add a DMZ to our network.
Currently, the internal network is connected to one ASA interface.
I have been able to set up a single device DMZ where one test laptop is directly connected to a spare ASA interface.  
I am trying to expand the experiment to include our existing switch so I can prove that two devices can reside inside the DMZ.
My question is:
Should I be using two interfaces on the ASA and running two cables to the switch?
Or, should I somehow be using only one ASA interface and one cable to the switch?
Or, should I be using two interfaces and two separate switches (one in the DMZ and one in the internal network)?
EXTRA DETAIL ABOUT THE SETUP
The environment is:

ASA 5505:

0/0:

outside
public facing IP
vlan2
security 0
connected to the serviced office building main network

0/1:  

inside
192.168.47.1
vlan1
security 100
connected to 0/0 on a ProCurve 2510G-48    

ProCurve 2510G-48:

DEFAULT_VLAN (came out of the box)

192.168.47.50
0/0:

uplink to the ASA 5505 0/1

The rest:

various servers 
another switch to which our desktops are connected

My initial experiment:

ASA 5505:

0/0:

outside
public facing IP
vlan2
security 0
connected to the serviced office buildings main network 

0/1:

inside
192.168.47.1
vlan1
security 100
connected to 0/0 on the ProCurve 2510G-48     

0/2:

dmz
192.168.48.1
vlan3
security 50
connected to TestLaptop1 with IP address 192.168.48.2

ProCurve 2510G-48:

As above

With NAT and access rules I got to the point where I can:

access the internet from TestLaptop1
access the TestLaptop1 from the internet
access one single device in the internal network from TestLaptop1 (to simulate limited internal access)
access TestLaptop1 from one single device in the internal network (to simulate management access)

I am now trying to add our existing switch into the mix.

A:

I wouldn't change the DMZ VLAN ID from 3 (5505) to 10 (2510) - depending on which protocols are active (GVRP, MVRP), this may cause problems.
If you tag VLAN3 on 5505 port 0/1 and 2510 port "0/0" (the first port should be "1") you can trunk both VLANs 1 and 3 on the same cable. Then, on the 2510, just config all required DMZ ports with VLAN3 untagged and they should be within the DMZ.

