Pretty quiet, just came back from a week there with the tinny, caught a few kg's over the sand/ weed patches but that was about it. Herring are pretty thin only got a couple over the whole week! Mind you had pretty average weather, blowing about 25knots for most of out stay. Fished down in dunsborough and managed to get some undersize kg's from the beach too! 

4x4 beaches- your best bet is wonnerup beach, about a 10 min drive north from the maccas in Busselton. Was really soft but you can do it without letting your tyres down. Took the tinny there and got bogged big time driving in off the track but used the recovery tracks and let the wheels down and had no problems from then on. We launched/retrieved there for the first time and had no issues. Lots of people also fish there off the beach during the early morning and late evening. Unfortunately thats the only one I can think of.

Cheers 

Salmon are rare in Geographe Bay this time of the year.
They generally start coming around Cape Naturaliste in numbers around Easter and that is when smaller schools (containing less than a dozen) pass through the bay. Reports of Salmon in Dunsborough or further South will be a few stragglers coming from the bigger resident schools from around Albany way.

Remember the Busselton Jetty almost points due North, so strong Southerly winds (offshore) make the bay look very flat, but once you venture out a few kms it can get real windy quick. In close you can move around the sand patches for a kg. Most will be undersized. Squid and Herring can be found at sunrise in the boat and again Herring closer to sunset.

You can get a feed of crabs if you work hard in the boat with the drop nets, or wade at night along the shore scooping.

The jetty can produce squid early morning and herring and tailor in the evening ... (further casts away from the jetty increase your chances of a hookup).

As Bruce says, 4x4 is available at Wonnerup beach about 7kms more East than North from the jetty, not far past the Geographe Marina. 4x4 on the beach is only permitted to the right of the Wonnerup carpark (opposite the flood gates) up to the mouth of the river (currently flowing and crossing the mouth is not possible nor permitted). Further East(well ENE) you can also access the beach closer to Forrest Beach (you'll have to get back on the bitumen at the Wonnerup carpark and head further ENE). Both beaches used to regularly produce whiting but far fewer recently. Evening beach fishing can produce small to medium sized tailor and herring.

Offshore, there is not much ground until you are out around the four mile reef (4 miles north from marina and extends West and East). Occasionally, just sized Dhuies can be caught there, but quite a few undersized ones in recent years. Plenty of fun can be had anchoring and berleying up on a small lump shown on the sounder with the prospect of skippy, Sambos, the odd shark, plenty of rock cods and wrasse and the odd (55cm+) thumper of a KG.
Further offshore there is an 8 mile reef. After that it's a fair distance (20+nm) out to deeper water with decent ground where you have a better chance of catching a good Dhuie.