My 2002 V6 usually sits aroun 60-70 when moving, rising to 90 in traffic
Have a look at www.gtvv6.com forum and there are several threads about
temperature.
(site is for TS, V6 and TB despite the V6 name)

To the chap from Hull,
My 1996 146ti 2 litre, water temp is always around 70 when driving, in slow
moving traffic it could go up to 90.
I thought it was low at first but I've had the car from new and I have
perfect performance and I get between 30 & 40 mph depending on the journey.
Don't worry about it.
Bill Jackson

Absolutely normal.
Alfa's cooling system is set up for Mediteranian temperatures.
Those Italians don't keep their heads cool, but do keep their engines cool.
So in our normal Western-Europe ambient temps the system is a bit over
dimensioned.

Some repliers say it's normal, but is isn't! It should be constantly 90?C if
it isn't, your thermostat has to be replaced. Had this problem to on my 145:
warm in slow traffic, cooling down during speeding at the highway. But now
it's fixed  with a new thermostat and temperature stays constant, no matter
what speed i'm driving or how cold it is outside.

So you better get a new thermostate, not that expencive but much better for
your engine to have a constant temperature.